As he left Washington Tuesday morning to travel to The Hague for the annual summit meeting of the NATO military alliance, President Trump was busy trying to hold together a fragile cease-fire between Israel and Iran. “Now we’re going to NATO and we’ll get a new set of problems,” Mr. Trump told reporters aboard Air Force One. “We’ll solve a new set of problems.”

The tentative cease-fire between Israel and Iran will likely dominate the agenda at the meeting, even as Russia continues to pummel Ukraine at the edge of the alliance’s territory. Mr. Trump is also expected to claim victory and assert that all NATO allies have agreed to spend 5 percent of their gross domestic product on their militaries, up from the current commitment of 2 percent. He has accused the allies of being overly dependent on the protection of U.S. forces.

“NATO was broke, and I said, ‘You’re going to have to pay,’ and we did a whole thing, and now they’re paying a lot,” he said.

But despite Mr. Trump's eagerness to take credit, not all countries have committed to the pledge. Spain, for example, has said it would not increase its spending above 2.1 percent of its G.D.P.

“They’re having a problem with Spain,” Mr. Trump said on Tuesday. “Always a problem with Spain. Spain’s not agreeing, which is very unfair to the rest of them.”

And yet Mr. Trump has maintained that the United States — which spends about 3.5 percent of its G.D.P. on its military — does not need to meet the 5 percent goal he has demanded of other countries. He argues that, for one thing, the United States does not have the same need to invest in its infrastructure to support military equipment.