Zelensky leaves Ukraine, heading to Munich to rally Western support.

President Volodymyr Zelensky of Ukraine chose not to cancel his scheduled trip out of the country Saturday to attend a security conference in Munich, even as warnings from the West about a Russian invasion of his country grew increasingly urgent.

Some observers in Washington have expressed concern that his leaving the country at this critical moment could provide an opening for Moscow, which the West believes is intent on toppling Mr. Zelensky’s government.

President Biden, asked whether it would be wise for Mr. Zelensky to leave, said on Friday that it was a judgment for the Ukrainian leader to make. Mr. Biden, who warned on Friday that President Vladimir V. Putin of Russia had made up his mind to attack Ukraine, said he had consulted with Mr. Zelensky a dozen times.

Despite his dire warning, Mr. Biden said there was still time for Mr. Putin to change his mind. And in that context, he said Mr. Zelensky’s trip to the Munich Security Conference, the annual trans-Atlantic security gathering being held this weekend, could be useful.

“In the pursuit of a diplomatic solution, it may — may be the wise choice,” he said. “But it’s his decision.”

Mr. Zelensky was meeting with Vice President Kamala Harris and other senior leaders from America’s NATO allies, including the leaders of Britain and Germany. His office said he expected “concrete agreements on providing our country with additional military and financial support to strengthen Ukraine’s resilience.”

In Britain, the office of Prime Minister Boris Johnson said the West was cooperating to ensure that any Russia incursion into Ukraine would be “met with strength, including significant economic consequences.”

Mr. Johnson and Mr. Zelensky agreed in their meeting that a further incursion “would be a profound miscalculation,” but that there was still room for Mr. Putin “to choose the path of peace and diplomacy,” Mr. Johnson’s office said.

Recognizing that some have been critical of the Ukrainian leader’s decision to leave the country for the event, Mr. Zelensky’s office noted that he planned to return on Saturday immediately after his meetings end.