President Donald Trump will embark on a whirlwind series of meetings this week at the United Nations General Assembly to make two big requests of the world: stand with us against North Korea, and hold the line against Iran’s nuclear program.

Over the course of four days beginning Monday, Trump will engage in a speed round of diplomacy that may test his patience for the notoriously factionalized, lethargic institution as well as his preference for one-on-one deal-making in which the U.S. always holds the strongest hand.

“Next week is not going to be short on topics,” the U.S. ambassador to the United Nations, Nikki Haley, said Friday. She acknowledged that foreign leaders are curious about how the unpredictable president will maneuver.

“They are all very anxious to hear what he has to say,” Haley said. “And I think that he will make quite an impact.”

Trump’s appearance at the U.N. — highlighted by a speech Tuesday — is his biggest moment on the world stage since taking office. There is far more at stake than at the two economic summits in Europe that he attended earlier this year. As he welcomes leaders from nearly 200 nations to his hometown of New York, he’ll press them to join U.S. efforts to constrain missile and nuclear programs in both North Korea and Iran.

Tensions have risen with both nations since Trump took office and assumed a more confrontational posture than Barack Obama’s.

“The world is still trying to take the measure of this president,” said Jon Alterman, senior vice president of the Center for Strategic and International Studies. “For a number of leaders, this is going to be their first chance to see him, to judge him, to try to get on his good side.”

Trump will hold a series of meetings with leaders from the Mideast, Latin America, Africa and Europe. He’ll give the major speech on Tuesday and host a diplomatic reception planned for Monday.

“I personally think he slaps the right people, he hugs the right people, and he comes out with the U.S. being very strong in the end,” Haley predicted.

Two key foreign leaders will not be on hand: Russian President Vladimir Putin and Chinese President Xi Jinping.

Obama is also expected to be in New York during the U.N. gathering, for an event sponsored by the Bill & Melinda Gates Foundation that will draw international figures.

The North Korean and Iranian nuclear programs are foremost on the president’s agenda. North Korea test-fired a ballistic missile with the range to reach Guam early on Friday, its latest in a series of provocations, and the Trump administration is seeking to extend and strengthen the Iranian nuclear deal that Obama signed and Trump has repeatedly maligned.

Trump will discuss the North Korea crisis over lunch with the leaders of South Korea and Japan. National security adviser H.R. McMaster said Friday that the world is “out of time” to stop North Korea from becoming a nuclear state.

Trump has a chance to surprise international leaders with a shift toward coalition-building on the world stage, Alterman said, noting Trump’s recent outreach to Democrats.

“He must look at it partly as an opportunity to have the world’s attention,” he said, “and partly it’s the world’s most tedious cocktail party.”