WASHINGTON — President Trump will fly to Singapore this month after all for a landmark summit meeting with North Korea’s leader, Kim Jong-un, but he now anticipates a more drawn-out negotiation than once envisioned and indicated that he will stop increasing pressure on the regime while talks proceed.

Eight days after abruptly canceling the June 12 meeting citing North Korea’s “open hostility,” Mr. Trump just as abruptly announced on Friday that it was back on, the latest head-spinning twist in a diplomatic drama that has captivated and confused much of the world. After complaining of North Korean bad faith, he said, in effect, never mind.

“We’re over that, totally over that, and now we’re going to deal and we’re going to really start a process,” Mr. Trump told reporters after meeting at the White House with a high-ranking North Korean envoy who delivered a personal letter from Mr. Kim. “We’re meeting with the chairman on June 12, and I think it’s probably going to be a very successful — ultimately, a successful process.”

He said that economic sanctions would remain in place in the meantime, but that he would not impose more as talks continue, and he even backed off the phrase “maximum pressure” that he has used to describe his strategy.