HANOI, Vietnam — The United States and North Korea offered conflicting accounts and traded blame on Thursday after a second summit meeting between President Trump and the North’s leader, Kim Jong-un, ended abruptly without any agreement on nuclear disarmament or easing tensions on the Korean Peninsula.

“Sometimes you have to walk,” Mr. Trump said at an afternoon news conference in Hanoi, the capital of Vietnam.

He said Mr. Kim had offered to dismantle the North’s most important nuclear facility if the United States lifted the harsh sanctions imposed on his nation — but would not commit to do the same for other elements of its weapons program.

That, Mr. Trump said, was a dealbreaker.

“It was about the sanctions,” Mr. Trump said. “Basically they wanted the sanctions lifted in their entirety, but we couldn’t do that.”