At U.N. Conference, Global Crises Collide With Fraught American Politics

President Biden will speak at a time of deep uncertainty about the future of America’s role in the world.

When President Biden addresses world leaders at the United Nations on Tuesday morning, his aides promise a speech filled with declarations about America’s role in shaping the future.

They say he will “reaffirm America’s leadership,” “rally global action” and provide “his vision for how the world should come together” on its most pressing challenges.

But the truth is that Mr. Biden will speak at a time of deep uncertainty about the future of America’s role in the world, including the war in Ukraine, escalating conflicts in the Middle East and growing economic competition with China.

Mr. Biden has vowed to continue pursuing a cease-fire that could end the fighting in Gaza, and his national security aides are feverishly working to forestall a broader war with Hezbollah in Lebanon. In Ukraine, Mr. Biden still faces urgent decisions, including whether to allow the use of American long-range weapons to strike deep into Russia.

And yet, there is a sense of precariousness when it comes to America’s longer-term intentions. Vice President Kamala Harris largely embraces Mr. Biden’s view of the importance of strategic alliances, though her specific policy views are still coming into focus as she campaigns on a compressed timeline. Former President Donald J. Trump promises a return to his “America First” brand of isolationism, while boasting about his own diplomatic skills.

The world leaders are gathering at the U.N. as multiple global crises are colliding with American politics in a way that could reshape how the United States confronts the world’s most difficult problems.

“For a world that is currently watching a war in Ukraine and a war in Gaza and the potential eruption of a war in Lebanon, where the United States is on this issue is both profoundly important and profoundly beyond their control,” said Jon B. Alterman, the director of the Middle East program at the Center for Strategic and International Studies in Washington.

Mr. Alterman said that for leaders of other nations, figuring out where America is headed after November’s elections “is one of the most important parts of their strategic calculus.”

To do that, many leaders are scrambling to meet with all three of America’s current or would-be leaders — Mr. Biden, Ms. Harris and Mr. Trump — during, or after, their visit to New York for the General Assembly this week.

The vice president had a closed-door meeting with Sheikh Mohammed bin Zayed, the president of the United Arab Emirates, at the White House on Monday afternoon, just hours after a similar meeting between the Emirati leader and Mr. Biden. Officials said Mr. Biden and Ms. Harris each was expected to raise the deepening violence in Israel and the Emirates’ involvement in the conflict in Sudan.

President Volodymyr Zelensky of Ukraine is set to meet with Mr. Biden in the Oval Office on Thursday, one day after he addresses the United Nations. Later on Thursday, Mr. Zelensky will meet separately at the White House with Ms. Harris — an indication that he is eager to bolster his own one-on-one relationship with her in case she wins the presidency in November.

After that meeting, aides say the White House has no plans for further engagement between Ms. Harris and foreign leaders or travel by the vice president outside the United States before Election Day, as she focuses all of her energies on the campaign trail.

There has been speculation about a possible Trump-Zelensky meeting as well, though a spokesman for the former president said on Monday that he had nothing to announce.

Mr. Trump has made no secret of his recent meetings with a steady stream of world leaders at his Mar-a-Lago estate in Palm Beach, Fla. On Sunday, he posted about a meeting with the emir and the prime minister of Qatar, who have been deeply involved in trying to negotiate peace between Israel and Hamas.

The emir “has proven to be a great and powerful leader of his country, advancing on all levels at record speed,” Mr. Trump wrote on social media after the meeting. “He is someone also who strongly wants peace in the Middle East, and all over the world. We had a great relationship during my years in the White House, and it will be even stronger this time around!”

During his time in office, Mr. Trump regularly questioned the need for decades-old alliances like NATO and abandoned newer ones, like the Paris climate accords and the Trans-Pacific Partnership.

Now, leaders in Europe, Asia and Africa are reading the tea leaves to see whether they can divine which future is likely to come to pass.

Will it be Ms. Harris’s interpretation of what Mr. Biden has called the “collective hope” of a world working together? Or will it be a return to bombastic threats from Mr. Trump, such as when he told the U.N. that he may “have no choice but to totally destroy North Korea”?

The stakes are high.

With Ukraine’s war against Russia entering its third year, Europe is actively confronting questions about its own security and whether it should wean itself from a longstanding reliance on American power as a guarantee against Russian aggression. Another Trump presidency is likely to force that debate to accelerate.

Mr. Biden is set to participate in a Security Council meeting on Ukraine on Tuesday that will include Mr. Zelensky. It will be a moment to underscore how successfully Mr. Biden has rallied much of the world to Ukraine’s side after Russia’s invasion in 2022.

In the Middle East, Mr. Biden’s steadfast support for Israel has left him more isolated among his global counterparts.

His diplomatic efforts have failed to bring an end to hostilities after the Hamas attacks in October that killed more than 1,200 people and left hundreds in captivity in Gaza. A recent escalation of violence between Israel and Hezbollah in Lebanon — including Israeli missiles attacks and exploding pagers that injured thousands of Hezbollah fighters — has prompted fears of a wider war.

John F. Kirby, the national security spokesman at the White House, said the president’s speech at the U.N. will outline “his vision for how the world should come together to solve these big problems and defend fundamental principles, such as the U.N. Charter.”

For the leaders in the audience, the question will be whether that vision is one that will continue after Jan. 20, Mr. Alterman said.

“The general attitude toward, ‘How does the world work and what role should the U.S. play in the world?’” he said, “strikes me as similar between Harris and Biden and fundamentally different between Biden and Trump.”