President Donald J. Trump will meet Chinese President Xi Jinping and Russian President Vladimir Putin together next week in Shenzhen, China, the White House said Friday, the first three-way meeting ever held among the leaders of the United States, China and Russia.

White House Assistant Press Secretary Olivia Wales told reporters on a call previewing the trip that the president will conclude his visit to China with the trilateral meeting on Thursday, Nov. 19, on the sidelines of the Asia-Pacific Economic Cooperation summit. Ms. Wales said the president has made clear that, among other topics, he will discuss reducing the world’s nuclear weapons, whose spread he considers very dangerous.

A senior administration official, speaking on condition of anonymity, said the president also intends to raise Iran at the meeting, according to Agence France-Presse and Anadolu Agency. Ukraine is not expected to be on the agenda, the official said, because China is not part of the separate track of talks between the United States and Russia.

“I would characterize this as the entry point, the first conversation, certainly at the leader level between these countries,” the official said, according to Anadolu Agency. The official said Washington does not expect an agreement to come out of the talks, described China’s nuclear arsenal as “growing by far the fastest in the world” and said it was time for Beijing to “step up to the adult table.”

Before the three-way session, Mr. Trump will hold a bilateral meeting and working lunch with Mr. Xi on Thursday afternoon, Ms. Wales said. It will be the fourth meeting between the two leaders since Mr. Trump returned to office, according to Agence France-Presse. Mr. Trump is not scheduled to hold a separate one-on-one meeting with Mr. Putin, officials said.

Mr. Xi is hosting this year’s APEC summit, which runs Nov. 18 and 19 in Shenzhen. The president will leave Washington on Monday and arrive in the Philippines on Tuesday for the summit of the Association of Southeast Asian Nations in Manila before traveling on to China, officials said. Elon Musk will accompany the president on the China trip but will not take part in the meeting with Mr. Xi and Mr. Putin, officials said.

The president had said on Sunday that he expected to meet the two leaders in Shenzhen to discuss “a lot of things, including denuclearization.”