President Trump met privately with President Volodymyr Zelensky of Ukraine on Saturday in Rome, the White House said, on the sidelines of the funeral service for Pope Francis. It was the first time the two leaders had met in person since their televised argument in late February in the Oval Office that resulted in a deep breach between the two countries.

The White House did not say when the two men met, but it appears likely it was before the funeral started, before the president left for the funeral services a little after 9 a.m. in Rome. A White House spokesman, Stephen Cheung, called it a “very productive discussion,” but gave no details.

The meeting in Rome came at a critical moment, just as the United States had presented a suggested plan for a cease-fire in Ukraine’s war with Russia and a postwar plan that would give Russia effective control over all of the lands it has illegally seized since the invasion began three years ago. The plan includes a major reversal of American policy: a formal American recognition that Crimea is Russian territory, even if Ukraine and the rest of Europe maintain that it remains part of Ukraine.

Mr. Trump had made clear he wanted his first trip overseas in this term to be to the Middle East, starting with Saudi Arabia, the site of his initial visit during his first term in office.

But then Pope Francis died. And so Saturday morning, made his way to Vatican City to pay his respects at the pontiff’s funeral.

As the ceremonies began, Mr. Trump was surrounded by European leaders he has been denouncing as freeloaders unwilling to pay their share of the continent’s defense, and leaders of the European Union, which he said was “formed in order to screw the United States.”