Twenty days ahead of a summit with Democratic People's Republic of Korea's leader Kim Jong-un planned for June 12, US President Donald Trump said on Tuesday it might not happen.

"There's a very substantial chance it won't work out," Trump said when he was asked about the conditions for meeting with Kim. "I don't want to waste a lot of time, and I'm sure he doesn't want to waste a lot of time. So there's a very substantial chance that it won't work out, and that's okay.

"That doesn't mean it won't work out over a period of time," Trump continued. "But it may not work out for June 12th. But there's a good chance that we'll have the meeting."

Trump made the remarks before meeting with South Korean President Moon Jae-in at the White House. It was the first time Trump raised doubts about the Singapore summit so explicitly.

Over the past few weeks he had either said he might walk out of the meeting if he is not satisfied, or said he will "see what happens", a tone that was maintained by the White House Press Secretary Sarah Sanders.

"We continue to prepare for the summit, and if they want to meet, we will certainly be ready," Sanders said at Tuesday's briefing.

The president himself is also personally preparing for the summit, according to Sanders. He has spent a significant amount of time meeting both in person and having regular phone conversations with other world leaders, and has constant and regular meetings with his national security team.

"This is something they talk about on a daily basis and will continue to in preparation," she said.

Overall, Trump is upbeat about the outcome of the summit. He has made promises again to guarantee the safety of the DPRK leader.

"It has a chance to be a great, great meeting for North Korea and a great meeting for the world," Trump said on Tuesday. "We will guarantee his safety. And we've talked about that from the beginning."

On Monday Trump tweeted that "China must continue to be strong & tight on the Border of North Korea until a deal is made."

Trump mentioned the border issue again on Tuesday, saying that "it's been opened up a little bit lately".

Answering a question about Trump's statement, Chinese Foreign Ministry spokesman Lu Kang said on Tuesday, "China has always strictly followed and fulfilled its due international obligations."

As a friendly neighbor to the DPRK, China has maintained normal exchange with it under the precondition of not violating its own international obligations, including in the economic and trade areas, Lu said, adding there is not necessarily a contradiction between the two things.

Moon said he is confident that Trump will be able to achieve a "historic feat of making the upcoming summit successful", promising that he will spare no effort to provide "all necessary support".

US Representative Steve Russell, a Republican from Oklahoma, said at a bipartisan congressional dialogue at the United States Institute of Peace, "I believe that it's in our best interest to continue to try to have the meeting and we can talk about what type of outcomes there would be."

Ted Lieu, another lawmaker, also said he hoped the summit would take place.

"I think there's incentive on both sides to try to have a summit; and I think there's incentive on both sides to declare victory and then go forward with the long process of getting to an eventual deal," the Democrat from California said at the discussion.

Contact the writer at?huanxinzhao@chinadailyusa.com

?