U.S. President Donald Trump and North Korea’s Kim Jong Un have failed to reach an agreement at their second summit in Vietnam, but talks between the two nations will continue in the future.

Trump explained the abrupt and early end to the summit by telling reporters: “Sometimes you have to walk.”

Trump said Thursday that North Korea wanted him to lift U.S. sanctions on the country in exchange for denuclearization, but he wasn’t willing to do that.

Still, he says Kim assured him he’ll continue to hold off on nuclear and missile tests.

U.S. Secretary of State Mike Pompeo said Thursday at the news conference in Hanoi that he wishes the two sides could have gotten further.

He says they asked Kim to do more and “he was unprepared to do that.”

The leaders had been expected to hold a working lunch as well as attend a joint agreement signing ceremony at the Hanoi Metropole hotel on Thursday. Instead, they departed in separate motorcades within minutes of each other after doing neither.

A joint agreement signing ceremony was scrapped.

Trump said he has not committed to a third summit with Kim. Trump told reporters “we’ll see if it happens,” but that he has “not committed.”

As for any further meetings, Trump says, “It might be soon. It might not be for a long time.”

Trump did not commit to saying the U.S. is demanding complete, verifiable and irreversible denuclearization of North Korea before removing sanctions on that country.

“I don’t want to put myself in that position from the standpoint of negotiation,” he said.

Trump and other U.S. officials have long maintained that denuclearization was a prerequisite to lifting sanctions on North Korea. Trump said earlier that U.S. sanctions were the sticking point in the talks with Kim.