Vice President Mike Pence has said the US made “zero concessions” in order to get an invitation to meet North Korean leader Kim Jong-un and talk about a possible end to Pyongyang’s nuclear weapons programme.

Mr Pence said that President Donald Trump has “consistently increased the pressure” on North Korea, which has continued the development of its weapons - including an increasing number of missile tests in the last 12 months - despite numerous resolutions by the United Nations. Later at the White House, the press secretary made it clear that talks would only take place if Washington saw “concrete action” by North Korea towards denuclearisation.

Mr Trump and Mr Kim are expected to meet before the end of May, although a date and location has yet to be set. After months of escalating rhetoric between the nations the prospect of a thaw has been welcomed by world leaders.

Ms Sanders said at a briefing on Friday that President Trump was “in a great mood” in the wake of the announcement, saying that the US was having conversations “from a position of strength” – with denuclearisation having always been the goal of the administration.

It has taken many by surprise, including US Secretary of State Rex Tillerson, who had said just hours before the announcement that the US was a “long ways from negotiations”.

But, Mr Tillerson said the President made the decision to accept the invite “himself”, a move he said was a “dramatic” reversal in posture for North Korea.

The swiftness of the more, allied to the lack of detail about the meeting, has led to questions about whether the summit may just play into the hands of Mr Kim, who will be given a rare photo opportunity with a prominent world leader, and get the type of international recognition that the regime craves.

In response to that Ms Sanders said that Mr Trump “is getting exactly what he wants” with Mr Kim having relayed to South Korea that Pyongyang had expressed a “commitment” to ending its nuclear programme, while also suggesting he would suspend any nuclear or missile tests during any direct talks.

”Let’s be very clear: the United States has made zero concessions. North Korea has made some promises,” Ms Sanders said. “We are making no concessions and we are not going to move forward until we see concrete and verified actions taken by North Korea.”

With both Mr Trump and Mr Kim involved, there is always likely to be an element of PR. “When diplomacy goes public there is an argument that it ceases to be diplomacy but merely an exercise in public relations,” said Dr Colin Alexander, an expert in political communications at Nottingham Trent University. “The meeting between the two leaders will be a carefully choreographed event... Just how much diplomatic substance will occur is debatable though,” he added.

North Korea indicates it could give up nuclear weapons, according to the South

But that symbolism was not lost on leaders around the world. Chinese President Xi Jinping told Mr Trump in a phone call on Friday that he “hopes the United States and North Korea start contacts and dialogue as soon as possible and strive to reach positive results,” according to state media.

A spokesperson for China’s Foreign Ministry Geng Shuang said that China supports “positive inter-Korean and US-North Korea interactions” and hopes that all parties “show their political courage” in order come back to the negotiating table.

In the 2000s, Beijing hosted several rounds of six-nation talks involving the Koreas, China, Russia, Japan and the US, armed at reducing Pyongyang’s nuclear programme.

Mr Trump has previously criticised China for not doing enough to push Pyongyang as North Korea’s major trading ally, but that tone has changed recently with China supporting the latest UN sanctions – the harshest ever imposed on the North.

However, China and Russia – another trading partner of Pyongyang – have been supporting the latest rounds of UN sanctions on the country.

After the invitation was extended and accepted, Foreign Minister Sergey Lavrov said the move was “a step in the right direction”.

He went on to express hope that an agreement would result from the meeting and that it is “necessary for normalising the situation around the Korean peninsula”.

Mr Lavrov had spoken out in January about the increasing “threats” the US had made about the potential of a military clash with North Korea in the wake of an increase in ballistic missile tests by Pyongyang during 2017, which suggested the Kim regime was close to developing a rocket capable of hitting the US.

“Everyone understands the catastrophic consequences of such recklessness,” Mr Lavrov said, apparently referencing Mr Trump’s tweet against North Korea, which included a number insulting Mr Kim by calling him “Rocket Man”.

North Korea – South Korea relations: in pictures Show all 21 1 /21 North Korea – South Korea relations: in pictures North Korea – South Korea relations: in pictures Pukguksong-2 missile - 2 May 2017 A solid-fuel "Pukguksong-2" missile lifts off during its launch test in North Korea on May 22, 2017. They said that it was examining operational plans for attacking Guam, an angry reaction to UN punishment for previous North Korean intercontinental ballistic missile tests and a US suggestion about preparations for possible preventive attacks to stop the North's nuclear weapons program. Korean Central News Agency/Korea News Service via AP North Korea – South Korea relations: in pictures Hwasong-12 -16 September 2017 North Korean leader Kim Jong-Un inspecting a launching drill of the medium-and-long range strategic ballistic rocket Hwasong-12 at an undisclosed location. Kim vowed to complete North Korea's nuclear force despite sanctions, saying the final goal of his country's weapons development is "equilibrium of real force" with the United States, state media reported on September 16, 2017. AFP/Getty Images North Korea – South Korea relations: in pictures Donald Trump address South Korean assembly - 7 November 2017 President Donald Trump talks with South Korean President Moon Jae-In during their joint press conference at the presidential Blue House on November 7, 2017 in Seoul.Trump was the first US President to address the South Korean National Assembly since President Clinton in 1993. He addressed Kim Jong Un warning him to not underestimate the US and that for talks to materialize then Pyongyang would need to take steps into denuclearization. Getty North Korea – South Korea relations: in pictures Demilitarized Zone Haean-Myeon, is a small military town near the Demilitarized Zone (DMZ) and border between North and South Korea, in Gangwon province. The zone is a strip of land running across the Korean Peninsula and was created after the 'Korean Armistice Agreement'. Any negotiations between the two countries tend to take place in this zone. AFP/Getty Images North Korea – South Korea relations: in pictures Declared state sponsor of terrorism by Trump - 20 November 2017 President Donald Trump speaks to the media during a cabinet meeting at the White House on November 20, 2017, where he officially designated North Korea as a state sponsor of terrorism. North Korea had previously been on the list, however was removed in 2008. Getty North Korea – South Korea relations: in pictures Hwasong-15 intercontinental ballistic missile - 29 November 2017 The North Korean government launches it's Hwasong-15 intercontinental ballistic missile at an undisclosed location in North Korea on November 29, 2017. It is supposedly capable of reaching all parts of the US. Korean Central News Agency via AP North Korea – South Korea relations: in pictures Hwasong-15 intercontinental ballistic missile - 29 November 2017 North Korean leader Kim Jong-Un celebrating the launch of the Hwasong-15 missile on November 29, 2017. AFP/Getty North Korea – South Korea relations: in pictures Kim Jong-Un New Year's speech - 1 January 2018 North Korean leader Kim Jong-Un delivering his New Year's speech. He vowed North Korea would mass-produce nuclear warheads and missiles in a defiant New Year message on January 1 suggesting he would continue to accelerate a rogue weapons programme that has stoked international tensions. Korean Central News Agency via AFP/Getty North Korea – South Korea relations: in pictures Intercontinental ballistic missile ice sculpture - 1 January 2018 Fireworks are seen above the Taedong River during New Year celebrations as visitors pose for a photo in front of an ice sculpture of an intercontinental ballistic missile at the Pyongyang Ice Sculpture Festival in Kim Il Sung Square in North Korea on 1 January, 2018. REUTERS North Korea – South Korea relations: in pictures US-South Korean military drills postponed - 4 January 2018 South Korean President Moon Jae-in talks with US President Donald Trump on January 4, 2018 in Seoul. South Korea and US agreed to delay the annual "Foal Eagle" military drills until after the PyeongChang Winter Olympic Games in an effort to "de-conflict" the Games and "focus on ensuring the security" of the event. South Korean Presidential Blue House via Getty North Korea – South Korea relations: in pictures North and South Korea have first official talks in over two years - 9 January 2018 Vehicles transporting the South Korean delegation, led by South Korean Unification Ministrer Cho Myoung-Gyon, drive past a checkpoint on the road connecting South and North Korea at the Unification Bridge, near the Demilitarized zone (DMZ) separating them both on January 9, 2018 in Paju. They began their first official face-to-face talks in two years. Getty North Korea – South Korea relations: in pictures North and South Korea have first official talks in over two years - 9 January 2018 Members of the South Korea delegation (R) shake hands with members of the North Korean delegation (L) during their meeting at the border truce village of Panmunjom in the Demilitarized Zone (DMZ) dividing the two Koreas on January 9, 2018. They focused on the forthcoming Winter Olympics after months of tensions over Pyongyang's nuclear weapons programme. AFP/Getty North Korea – South Korea relations: in pictures Foreign Ministers Meeting on Security and Stability on the Korean Peninsula - 16 January 2018 Foreign Ministers from twenty countries from North and South America, Asia, and Europe pose for a photo at the Vancouver Foreign Ministers Meeting on Security and Stability on the Korean Peninsula, in Vancouver on January 16, 2018. The US urged an escalation in pressure on North Korea over its nuclear missile program, despite a more cautious tone from key US ally South Korea. Secretary of State Rex Tillerson, co-hosted the event with Canada's foreign minister Chrystia Freeland, and called for North Korean ships to be intercepted and for new punitive measures to be implemented every time Pyongyang tests new weapons. AFP/Getty North Korea – South Korea relations: in pictures North Korea and South Korea to march together at Winter Olympics - 20 January 2018 PyeongChang 2018 Olympics President Lee Hee-beom, North Korea's Sports Minister and Olympic Committee president Kim Il Guk, International Olympic Committee President Thomas Bach, South Korean Minister of Culture, Sports and Tourism Do Jong-hwan and South Korea's National Olympic Committee President Lee Kee-heung join their hands as they pose during a signing ceremony at the Olympic Museum on January 20, 2018 in Lausanne. North Korea will send 22 athletes to the Winter Games in the South. The two nations will also march together at the opening ceremony. AFP/Getty North Korea – South Korea relations: in pictures Anti-North Korea activists protest delegation arrival - 22 January 2018 Anti-North Korea activists burn a portrait of leader Kim Jong-Un during a rally Seoul Station as a North Korean delegation arrived to check out performance venues for the Winter Olympics on January 22, 2018. Protesters led by the Korean Patriots Party gathered and complained that the talks to encourage North Korea's participation is stealing the spotlight from their country to the benefit of the regime. Donga Daily via Getty North Korea – South Korea relations: in pictures Panmunjom - 7 February 2018 South Korean soldiers stand guard at the border village of Panmunjom in the Demilitarized Zone (DMZ) between South and North Korea on February 7, 2018. In a sign of thawing bilateral ties, North Korea today announced that Kim Yo-jong, the sister of North Korean leader, Kim Jong-un, will attend the opening ceremony of the PyeongChang Winter Olympic Games. Getty Images North Korea – South Korea relations: in pictures North Korean ferry arrives in South Korea - 6 February 2018 North Korean ferry Mangyongbong-92 carrying a 140-strong orchestra approaches a port in Donghae, South Korea, February 6, 2018. REUTERS North Korea – South Korea relations: in pictures Anti-North Korea protest - 6 February 2018 A member of a conservative civic group tears a portrait of North Korean leader Kim Jong Un during an anti-North Korea protest as the North Korean ferry Mangyongbong-92 carrying a 140-strong orchestra approached. REUTERS North Korea – South Korea relations: in pictures North Korea at the athletes village - 8 February 2018 A North Korean flag is seen hanging on a building at the Winter Olympics athletes village in Gangneung, South Korea. REUTERS North Korea – South Korea relations: in pictures Olympic Welcome ceremony - 8 February 2018 Democratic People's Republic of Korea Vice Sports Minister Won Gil-woo receives a gift from mayor of the Olympic Village Kim Ki-hoon during the welcome ceremony ahead of the PyeongChang 2018 Games at the Olympic Village on 8 February, 2018 in South Korea. Getty Images North Korea – South Korea relations: in pictures Mike Pence meets Moon Jae-in - 8 February 2018 US Vice President Mike Pence shakes hands with South Korean President Moon Jae-in before their meeting at the presidential office in Seoul, South Korea on 8 February, 2018. REUTERS

The EU also welcomed the announcement about the meeting, calling it a “positive development”.

EU foreign policy chief Federica Mogherini, in a statement, said that “the complete, verifiable and irreversible denuclearisation of the Korean Peninsula” is hopefully the outcome.

She also welcomed another summit planned for April between Mr Kim and South Korea’s President Moon Jae-in to take place near the border between the two Koreas.

German Chancellor Angela Merkel said news of the possible meeting gave reasons to be hopeful about Korea. “Regarding North and South Korea and also the possibility of a meeting with the President of the United States, you can see that a cohesive international position, including sanctions, can lead to glimmers of hope,” she said.

South Korean Foreign Minister Kang Kyung-wha said South Korea will make sure if the US summit does take place, “it’s a meaningful meeting with good outcome.”

Ms Kang noted that the “the exact timing and the place [of the US summit] will need a lot of consideration”.

“Well done, President Trump. You’re on the way to a historical meeting no US president has ever done,” former NBA star Dennis Rodman told the Associated Press. Mr Rodman is one of very few Americans to have met Mr Kim and did so twice – in 2013 and 2014. He said he hoped for a return trip for more of his “basketball diplomacy”.

Though Republicans in Congress also praised the diplomatic tactics of the US for getting the invitation and cited it as proof that sanctions against Pyongyang were working, not everyone was optimistic about the meeting.

Democratic Senator Ed Markey said Mr Trump should treat it “as the beginning of a long diplomatic process” and his usual “unscripted” remarks and inflammatory tweets that could derail it.

The top Democrat on the House Intelligence Committee, Adam Schiff, said the Republican president would need help from others in the U.S. government if he is to go head-to-head with Kim over such a complex issue as nuclear weapons and geostrategy.