Will Trump change his mind about NATO?

Will Trump change his mind about NATO? 01:51

Will Trump change his mind about NATO?

(CNN) When US President Donald Trump attends his first NATO summit in Brussels on Thursday, the Manchester terror attack will be uppermost in the minds of the 28 leaders around the table.

Even before the atrocity, the US President wanted to push NATO allies to commit to a greater role in counter-terrorism and the fight against ISIS in Syria and Iraq. Monday's concert bombing will bring renewed urgency to that discussion.

European NATO leaders are approaching this summit with trepidation. During his campaign for the White House, Trump sent ripples of alarm through the continent when he described the 68-year alliance as "obsolete" because it did not do enough to tackle one of the greatest challenges facing the world: Islamist terrorism.

Though he has backtracked since becoming President by declaring it not obsolete, NATO allies in Europe remain concerned and want him to make a full commitment to Article 5 of the North Atlantic Treaty , which states that an attack on one member is deemed to be an attack on all.

Tied to this concern are the links between the Trump administration and Russia, the country seen as the greatest threat to European stability by NATO allies on this side of the Atlantic.

"It is not unusual for the first summit for a new US President to be a 'get to know you' summit -- but there is a bit more at stake," said Sophia Besch, a NATO expert at the Centre for European Reform.

European allies had to take Trump's "obsolete" comments "very seriously," Besch said, because Europe depends on America's defense capabilities and contribution to NATO -- US currently provides 22% of the organization's budget, while Germany gives 15% and the UK provides 10%.

Other NATO members have a target of 2% of GDP on defense spending, but only a minority have met this target. She added: "Trump has never formally committed to Article 5 because he doesn't accept that Russia may be a threat to Europe."

If other NATO states can show they are doing more on counter-terrorism and burden-sharing, Trump is expected to commit to the alliance. But the question of relevance still lingers.

Photos: President Trump's first foreign trip President Donald Trump and first lady Melania Trump board Air Force One on Saturday, May, 27, 2017, at Naval Air Station Sigonella in Italy. They were headed back to the United States after a nine-day trip to the Middle East and Europe. Hide Caption 1 of 69 Photos: President Trump's first foreign trip President Trump greets people on May 27, after speaking to US troops at Naval Air Station Sigonella. Hide Caption 2 of 69 Photos: President Trump's first foreign trip President Trump addresses US troops and their families on May 27, at the Sigonella Naval Air Station. Hide Caption 3 of 69 Photos: President Trump's first foreign trip President Trump and first lady Melania Trump arrive on May 27, to address US military personnel and families at Naval Air Station Sigonella. Hide Caption 4 of 69 Photos: President Trump's first foreign trip Leaders of the G-7 and some African nations pose for a photo on May 27, on the second day of the G-7 summit in Taormina, Italy. Hide Caption 5 of 69 Photos: President Trump's first foreign trip President Trump gestures on May 27, during a G-7 session. Hide Caption 6 of 69 Photos: President Trump's first foreign trip President Donald Trump and his wife, Melania, arrive for a concert of the La Scala Philharmonic Orchestra while in Taormina, Italy, on Friday, May 26. The Trumps are in Italy for a two-day G-7 summit. Hide Caption 7 of 69 Photos: President Trump's first foreign trip Trump and other leaders pose for a group photo at the G-7 summit on May 26. From left are European Council President Donald Tusk, Canadian Prime Minister Justin Trudeau, German Chancellor Angela Merkel, Trump, Italian Prime Minister Paolo Gentiloni, French President Emmanuel Macron, Japanese Prime Minister Shinzo Abe, British Prime Minister Theresa May and European Commission President Jean-Claude Juncker. Hide Caption 8 of 69 Photos: President Trump's first foreign trip Trump and Trudeau walk together after the group photo. Hide Caption 9 of 69 Photos: President Trump's first foreign trip G-7 leaders congregate during a walking tour on May 26. Hide Caption 10 of 69 Photos: President Trump's first foreign trip Trump embraces new French President Emmanuel Macron on May 26. Hide Caption 11 of 69 Photos: President Trump's first foreign trip The leaders watch a French air squadron. Hide Caption 12 of 69 Photos: President Trump's first foreign trip Melania Trump arrives at the City Hall in Catania, Italy, on May 26. She was wearing a $51,500 Dolce & Gabbana jacket as she met with other spouses of G-7 leaders. Hide Caption 13 of 69 Photos: President Trump's first foreign trip Trump shakes hands with Macron in Brussels, Belgium, on Thursday, May 25. They were attending a NATO summit as the alliance officially opened a new $1 billion headquarters. Hide Caption 14 of 69 Photos: President Trump's first foreign trip Trump stands with other world leaders during a NATO photo shoot on May 25. Hide Caption 15 of 69 Photos: President Trump's first foreign trip Trump speaks with British Prime Minister Theresa May during a working dinner at NATO headquarters. Hide Caption 16 of 69 Photos: President Trump's first foreign trip Trump stands next to German Chancellor Angela Merkel at the NATO summit. Hide Caption 17 of 69 Photos: President Trump's first foreign trip Melania Trump visits the Magritte Museum in Brussels with Amelie Derbaudrenghien, partner of Belgian Prime Minister Charles Michel. Hide Caption 18 of 69 Photos: President Trump's first foreign trip A girl takes a selfie with Melania Trump at a children's hospital in Brussels on May 25. Hide Caption 19 of 69 Photos: President Trump's first foreign trip Trump meets with Macron in Brussels. Hide Caption 20 of 69 Photos: President Trump's first foreign trip Trump walks with European Council President Donald Tusk, center, and European Commission President Jean-Claude Juncker, right, after they met at the European Council in Brussels on May 25. Hide Caption 21 of 69 Photos: President Trump's first foreign trip Trump, third from right, attends a meeting with leaders at the European Council. Hide Caption 22 of 69 Photos: President Trump's first foreign trip Trump speaks with King Philippe of Belgium as Queen Mathilde and Melania Trump chat during a reception at the Royal Palace in Brussels on Wednesday, May 24. Hide Caption 23 of 69 Photos: President Trump's first foreign trip Tusk talks to Trump as he welcomes him in Brussels. Hide Caption 24 of 69 Photos: President Trump's first foreign trip Trump stands with Belgian Prime Minister Charles Michel while the national anthem is played during Trump's arrival in Belgium on May 24. Hide Caption 25 of 69 Photos: President Trump's first foreign trip Protesters in Brussels demonstrate with effigies of Trump and Michel on May 24. Hide Caption 26 of 69 Photos: President Trump's first foreign trip Trump shakes hands with Italian President Sergio Mattarella in Rome on May 24. Hide Caption 27 of 69 Photos: President Trump's first foreign trip Pope Francis stands with Trump and his family during a private audience at the Vatican on May 24. Joining the President, from left, are Trump's son-in-law, White House senior adviser Jared Kushner; Trump's daughter and adviser Ivanka Trump; and first lady Melania Trump. Hide Caption 28 of 69 Photos: President Trump's first foreign trip Trump and the Pope exchange gifts. Trump presented the Pope with a first-edition set of Martin Luther King's writings. The Pope gave Trump an olive-tree medal that the Pope said symbolizes peace. Hide Caption 29 of 69 Photos: President Trump's first foreign trip Trump and his wife look at the ceilings of the Sistine Chapel. Hide Caption 30 of 69 Photos: President Trump's first foreign trip Trump speaks to reporters in Rome during a meeting with Italian Prime Minister Paolo Gentiloni, right, on May 24. Hide Caption 31 of 69 Photos: President Trump's first foreign trip The first lady visits a pediatric hospital in Vatican City on May 24. Hide Caption 32 of 69 Photos: President Trump's first foreign trip Melania Trump arrives at the Vatican on May 24. With Vatican protocol in mind, she wore a black veil and long-sleeved black dress draped down to her calf. Ivanka Trump wore a similar outfit with a larger veil. Hide Caption 33 of 69 Photos: President Trump's first foreign trip President Trump and Israeli Prime Minister Benjamin Netanyahu wave at the Israel Museum in Jerusalem on Tuesday, May 23. Trump gave a speech there, reaffirming his country's commitment to Israel while also holding up Judaism's historical ties to the United States. Hide Caption 34 of 69 Photos: President Trump's first foreign trip People take pictures of the message Trump wrote at Yad Vashem, the Holocaust memorial in Jerusalem, on May 23. Hide Caption 35 of 69 Photos: President Trump's first foreign trip With the help of US Marines, Trump and his wife lay a wreath at Yad Vashem. Hide Caption 36 of 69 Photos: President Trump's first foreign trip Trump meets with Mahmoud Abbas, the President of the Palestinian Authority, on May 23. Trump met with Israeli leaders the day before and said he believes both sides "are ready to reach for peace." Hide Caption 37 of 69 Photos: President Trump's first foreign trip A Palestinian security official takes position before the arrival of Trump's convoy in Bethlehem, West Bank. Hide Caption 38 of 69 Photos: President Trump's first foreign trip Israeli and American activists hold signs Monday, May 22, during an anti-Trump protest next to the US embassy in Tel Aviv, Israel. Hide Caption 39 of 69 Photos: President Trump's first foreign trip Melania Trump and Israeli first lady Sara Netanyahu speak to children during their visit to the Hadassah hospital in Jerusalem on May 22. Hide Caption 40 of 69 Photos: President Trump's first foreign trip Trump talks to reporters as he meets with Israeli Prime Minister Benjamin Netanyahu on May 22. Trump sought to rebut claims that he damaged Israeli intelligence capabilities by revealing highly classified information to Russian operatives earlier this month. "Just so you understand, I never mentioned the word or the name Israel," Trump told reporters as he began the second leg of his first foreign tour. Hide Caption 41 of 69 Photos: President Trump's first foreign trip Trump touches the Western Wall, Judaism's holiest prayer site, while in Jerusalem on May 22. Trump became the first sitting US president to visit the wall. Hide Caption 42 of 69 Photos: President Trump's first foreign trip Trump stands in the Western Wall plaza. To his left, in black, is Shmuel Rabinowitz, the rabbi of the Western Wall. Hide Caption 43 of 69 Photos: President Trump's first foreign trip First lady Melania Trump, in white, visits the Western Wall. At far left is Ivanka Trump. Hide Caption 44 of 69 Photos: President Trump's first foreign trip The President and first lady plant a tree in Jerusalem with Israeli President Reuven Rivlin. Hide Caption 45 of 69 Photos: President Trump's first foreign trip Trump is welcomed by Netanyahu upon arriving in Tel Aviv on May 22. Trump started his trip with two days in Saudi Arabia. Hide Caption 46 of 69 Photos: President Trump's first foreign trip On the way to Tel Aviv, US Secretary of State Rex Tillerson speaks with reporters aboard Air Force One. Hide Caption 47 of 69 Photos: President Trump's first foreign trip While in Riyadh, Saudi Arabia, Trump attends the inauguration ceremony for the Global Center for Combating Extremist Ideology. Joining him here are Saudi King Salman bin Abdulaziz Al Saud, center, and Egyptian President Abdel Fattah el-Sisi, left. Hide Caption 48 of 69 Photos: President Trump's first foreign trip Trump speaks in Riyadh during the Arab Islamic American Summit on Sunday, May 21. Trump looked to make it clear that the United States is not at war with Islam. "This is not a battle between different faiths, different sects or different civilizations," he said. "This is a battle between barbaric criminals who seek to obliterate human life, and decent people of all religions who seek to protect it. This is a battle between good and evil." Hide Caption 49 of 69 Photos: President Trump's first foreign trip Trump sits at the summit, which included leaders from 55 Muslim-majority countries. He urged them to do more to eradicate terrorist groups that claim the mantle of Islam. "We can only overcome this evil if the forces of good are united and strong and if everyone in this room does their fair share and fulfills their part of the burden," Trump said. "Muslim-majority countries must take the lead in stamping out radicalization." Hide Caption 50 of 69 Photos: President Trump's first foreign trip Trump poses with other leaders at the Arab Islamic American Summit. Hide Caption 51 of 69 Photos: President Trump's first foreign trip Saudi King Salman shakes hands with Trump on May 21. Trump is the first US president to start his first foreign trip in the Middle East. Hide Caption 52 of 69 Photos: President Trump's first foreign trip Trump meets with other heads of state in Riyadh on May 21. Hide Caption 53 of 69 Photos: President Trump's first foreign trip Trump speaks with the Crown Prince of Abu Dhabi, Gen. Sheikh Mohammed Bin Zayed Al Nahyan. Hide Caption 54 of 69 Photos: President Trump's first foreign trip First lady Melania Trump chats with children during a visit to the American International School in Riyadh on May 21. Hide Caption 55 of 69 Photos: President Trump's first foreign trip While in Riyadh, President Trump meets with Bahrain's King Hamad bin Isa Al Khalifa on May 21. Hide Caption 56 of 69 Photos: President Trump's first foreign trip President Trump and Egyptian President Abdel Fattah el-Sisi share a laugh during a meeting on May 21. El-Sisi complimented Trump on his "unique personality that is capable of doing the impossible." Trump exchanged pleasantries back, praising el-Sisi's shoes. Hide Caption 57 of 69 Photos: President Trump's first foreign trip Trump is handed a sword during a welcoming ceremony at Riyadh's Murabba Palace on Saturday, May 20. Hide Caption 58 of 69 Photos: President Trump's first foreign trip Trump sits with members of his staff and Cabinet before a meeting with Saudi King Salman on May 20. Hide Caption 59 of 69 Photos: President Trump's first foreign trip Trump and King Salman take part in a signing ceremony at the Saudi Royal Court in Riyadh on May 20. The two leaders oversaw the signing of a defense deal worth nearly $110 billion. Hide Caption 60 of 69 Photos: President Trump's first foreign trip The Trumps look at a display of modern art at the Saudi Royal Court in Riyadh. Hide Caption 61 of 69 Photos: President Trump's first foreign trip King Salman presents Trump with a gilded necklace and medal, the country's highest honor. The distinction also was bestowed upon Presidents Barack Obama and George W. Bush. Hide Caption 62 of 69 Photos: President Trump's first foreign trip The first lady chats with Saudi Crown Prince Muhammad bin Nayef at the medal ceremony on May 20. Hide Caption 63 of 69 Photos: President Trump's first foreign trip Ivanka Trump attends the medal ceremony. Hide Caption 64 of 69 Photos: President Trump's first foreign trip Trump meets with King Salman after arriving in Riyadh on May 20. Hide Caption 65 of 69 Photos: President Trump's first foreign trip Soldiers on horseback carry the US and Saudi flags as they escort Trump to the Saudi Royal Court in Riyadh. Hide Caption 66 of 69 Photos: President Trump's first foreign trip Trump is welcomed by King Salman after arriving at the King Khalid International Airport in Riyadh. Hide Caption 67 of 69 Photos: President Trump's first foreign trip The Trumps take part in the welcome ceremony. Hide Caption 68 of 69 Photos: President Trump's first foreign trip The President and first lady wave from Air Force One after landing in Riyadh. Hide Caption 69 of 69

NATO as an organization cannot prevent the kind of terror attack that took place in Manchester, Besch said, but can focus on tackling ISIS in the Middle East.

"We can expect NATO leaders to discuss Manchester as an example of the threat of terrorism in Europe," Besch added. "What they can do, what they are doing but should perhaps invest more resources and personnel in, is engagement in unstable countries like Iraq, Afghanistan, or perhaps even Libya, through training of armed forces and police.

"They should also get much better at intelligence and information sharing, not just between NATO allies, but also between NATO and the EU."

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Last year, NATO recognized cyber warfare as an official front, and is taking steps to deal with the shifting challenge of terrorism. But while counter-terrorism and spending were key issues, European allies want to ensure Trump does not divert attention away from Russia, according to Patricia Lewis, head of the International Security Department at Chatham House.

The key question was "how much does the US set the agenda for NATO and how do you prevent divergence between NATO's European partners and Canada and the US," Lewis told CNN.

Russia will be on the agenda and there were signs that "behind the scenes Trump is prepared to talk about things," Lewis said.

"Article 5 is the bottom line for NATO -- that is what NATO is all about. The one and only time Article 5 has ever been invoked was on 9/11; that was in the defense of the US," Lewis added.

"Smaller countries can all show that they are doing a lot in terms of contribution. More importantly, if NATO capability is something that can only be provided by the US, and the rest of NATO can work in partnership only with the US, then that is where the problem is."

Trump's "obsolete" comment, Lewis said, may have been him "trying to grab the attention of NATO states and to urge them to step up and say 'this is about security, don't expect the US to always be there whatever.'"