Biden will meet the NATO leader at the White House today.

President Biden is hosting the NATO secretary general, Jens Stoltenberg, at the White House on Tuesday afternoon to discuss long-term strategy in Ukraine and who will oversee the 31-member military alliance moving forward.

The visit comes during a critical time for the Western alliance, as Ukraine mounts a counteroffensive to regain territory claimed by Russia and as NATO members prepare for a summit next month in Vilnius, Lithuania. The White House has also in recent weeks faced questions over whom Mr. Biden supports as a successor for Mr. Stoltenberg, who has led the alliance since 2014 and is expected to step down in September.

“The president believes that whoever is the secretary general of NATO should be an individual who the entire alliance can get behind and lead the alliance into the future, because there’s a transformative future ahead of the alliance,” John Kirby, a spokesman for the National Security Council, said on Monday. “Whenever this war ends, however it ends, NATO is going to be different.”

Various nations are jockeying for their own officials to succeed Mr. Stoltenberg and Mr. Biden’s opinion brings considerable weight since the United States spends more than any other member of the alliance on defense.

While the British prime minister, Rishi Sunak, was visiting Washington last week, Mr. Biden was asked whether it was time for a British official to lead NATO. “That remains to be seen,” he said.

Mr. Biden also recently met with Mette Frederiksen, the prime minister of Denmark and another potential contender for the position.

The meeting with Mr. Stoltenberg was initially scheduled for Monday, but Mr. Biden had to postpone it for a day so he could have a root canal.

The meeting also comes as some Republican members of Congress debate how — or whether — to provide future U.S. aid to Kyiv. Mr. Biden has said the United States is committed to assisting Ukraine.

“We are continuing to talk to the Ukrainians about some of their long-term defense needs and what that needs to look like,” Mr. Kirby said on Monday, noting that even after the war ends, “Ukraine is going to have legitimate security needs with a long border with Russia.”