The announcement on Wednesday came after a meeting between US Secretary of State Mike Pompeo and North Korean officials supposed to have taken place this week was rescheduled.
Pompeo had been due to hold talks in New York on Thursday with senior North Korean official Kim Yong-Chol aimed at paving the way for a second Kim-Trump summit and at making progress on denuclearisation.
The State Department said the meeting had been postponed but gave no reason, raising concerns talks aimed at persuading North Korea to give up its nuclear arms could break down. The State Department said the talks would be rescheduled “when our respective schedules permit”.
Trump told a White House news conference the change was “because of trips that are being made”, but did not elaborate on these.
“We are going to make it … another day,” he said. “But we’re very happy with how it’s going with North Korea. We think it’s going fine. We’re in no rush.”
Trump said he still expected to hold a second summit with Kim. “Sometime next year, I would say. Sometime early next year,” he said.
Kim pledged to work towards denuclearisation at an unprecedented first meeting with Trump in Singapore but negotiations have made little headway since, with North Korea falling short of US demands for irreversible moves to abandon a weapons program that potentially threatens the United States.
Pyongyang has complained that Washington has not made concessions in return for the moves it has taken and last Friday warned it could resume development of its nuclear programme if the US did not drop its sanctions campaign.
The Trump administration has said that sanctions will not be lifted until North Korea gives up its weapons.
“The sanctions are on … I’d love to take the sanctions off, but they [North Korea] have to be responsive, too,” Trump said on Wednesday.
South Korea, which has worked to encourage US-North Korea dialogue, sought to play down the talks delay.
South Korean Foreign Minister Kang Kyung-wha said on Thursday the North had suggested a postponement. “The North side said ‘both of our schedules are busy, so let’s postpone’,” Kang said, according to what she was told by the United States.