Trump raised doubts about the Singapore summit in talks with South Korean President Moon Jae-in, who came to Washington to urge Trump to not let a rare opportunity with the reclusive North Korea slip away.

If the summit is called off or fails, it would be a major blow to what Trump supporters hope will be the biggest diplomatic achievement of his presidency, and a huge disappointment for the President himself.

“And you know, there’s a chance that it will work out. There’s a chance, there’s a very substantial chance, that it won’t work out. 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. But it may not work out for June 12th. But there’s a good chance that we’ll have the meeting,” Trump told reporters at the White House.

South Korea’s Moon Jae-in said, “And we find ourselves standing one step closer to the dream of achieving complete denuclearization on the Korean peninsula and world peace. All this was possible because of you, Mr. President, and I have no doubt that you will be able to complete, accomplish, a historic feat that no one had been able to achieve in the decades past. I have to say that the fate and the future of the Korean peninsula hinge on this and, as such, I’ll spare no effort to the end to support the success of the upcoming U.S.-North Korea summit and stand with you all along the way.”