Much has been made of President Donald Trump's visits to Saudi Arabia and Israel this week, but high-stakes meetings are still to come — in Europe. The president heads to Rome on Tuesday, after he spent the start of his first foreign trip in the Middle East talking about efforts to combat terrorism and seek peace between Israel and the Palestinians. In the ensuing days, Trump will meet with Pope Francis, top European Union officials, leaders of NATO member countries and the leaders of the Group of 7 economic powers. For Trump, the meetings yield an opportunity to follow through on pledges: to push European allies to spend more on defense and to strike a more coordinated effort against North Korea, among other issues. On the European side, the meetings are a chance to gauge Trump's loyalty — or lack of it — to the Continent. The American president has repeatedly bashed institutions like the EU and NATO that have formed the basis of U.S.-Europe cooperation for decades.

'Will the real Trump please stand up?'

"I think that European leaders will, in part, be asking, 'Will the real Trump please stand up? Is America under your leadership going to remain the stalwart ally it has been since Pearl Harbor?'" said Charles Kupchan, a senior fellow at the Council on Foreign Relations and former National Security Council official in the Obama and Clinton administrations. Trump won the White House last year with an anti-global, inward-looking message. He pledged to pull out of free trade deals he deemed bad for American workers, to crack down on immigration and to avoid costly military entanglements.

His foreign policy alarms Europe. Trump cheered the British referendum to leave the EU last year and more subtly backed anti-EU French presidential candidate Marine Le Pen this year. He called NATO — the 28-member defense alliance that won the Cold War — "obsolete." Trump sought better relations with Russia, a largely autocratic country that attacked Ukraine in 2014 and which is widely believed to disrupt Western countries' democratic elections.

NATO 'no longer obsolete'?

Trump has at least temporarily backpedaled on his most inflammatory rhetoric, saying last month that NATO is "no longer obsolete." Separately last month, he said that a "strong Europe" is important for the United States. European leaders want to know where the unpredictable American president stands on the importance of alliances. "The case for close and sustained trans-Atlantic cooperation has never been stronger," a spokesman for the European Commission — the EU's executive branch, whose president, Jean-Claude Juncker, will meet with Trump — told reporters last week when asked about the U.S. president.

One event during Trump's European stop may hold particular significance, according to Constanze Stelzenmueller, the Robert Bosch senior fellow at the Brookings Institution. In Brussels on Thursday, Trump will participate in the unveiling of a NATO memorial representing in part the only time the treaty's mutual defense clause, Article 5, was put into effect, which was after the Sept. 11, 2001, attacks to aid the United States. Trump has complained that most NATO allies do not pay the 2 percent of gross domestic product that's required of them by agreement. He created particular alarm, though, by not committing to honoring Article 5 if a U.S. ally gets attacked, despite protests from top administration officials. When Trump unveils the memorial related to Article 5 assistance for the U.S., allies are partly "calling his bluff," Stelzenmueller said.

Trump looks for 'concrete wins'