The Trump White House expressed cautious optimism over the outcome of the historic inter-Korean summit on Friday, saying "good things are happening" on the peninsula, while warning that its pressure campaign will continue unabated.

Meanwhile, US President Donald Trump lauded his Chinese counterpart Xi Jinping's efforts on the Democratic People's Republic of Korea, calling them a "great help".

In their Friday summit at the border village of Panmunjom, the Republic of Korea President Moon Jae-in and DPRK top leader Kim Jong-un agreed to pursue a permanent peace treaty and the complete denuclearization of their divided peninsula.

"KOREAN WAR TO END!" Trump tweeted on Friday. "The United States, and all of its GREAT people, should be very proud of what is now taking place in Korea!"

"Please do not forget the great help that my good friend, President Xi of China, has given to the United States, particularly at the Border of North Korea. Without him it would have been a much longer, tougher, process!" Trump said in another tweet.

Trump seemed to be taking the credit for what is happening on the peninsula, hinting that he has accomplished mission impossible.

"When I began, people were saying that was an impossibility," Trump said when meeting with US athletes who participated in this year's Winter Olympics in South Korea. "They said there were two alternatives: Let them have what they have, or go to war. And now we have a much better alternative than anybody thought even possible."

He made it clear that his meeting with Kim will soon happen. "I'll be meeting with Kim Jong-un in the coming weeks as we seek to denuclearize the North Korean area and the entire Korean Peninsula," Trump said.

He even narrowed the number of possible sites for his upcoming summit to only "two or three" from an earlier five.

But he was more cautious in tone when he welcomed German Chancellor Angela Merkel to the Oval Office. "We're not going to be played, okay? We're going to hopefully make a deal," he told reporters. "And if we don't, we leave the room."

In another tweet sent on Friday, Trump said "good things are happening, but only time will tell."

US Vice-President Mike Pence said the Korean peace agreement is a just one step toward denuclearization of the Korean Peninsula.

"Planning for the United States and North Korea Summit continues, but as we've said before – the pressure campaign will continue unabated," Pence said in a statement.

US Secretary of State Mike Pompeo, while congratulating on the historic inter-Korean meeting, also said in Brussels, "We're committed to permanent, verifiable, irreversible dismantling of North Koreans' weapons of mass destruction programs without delay. Until then, the global maximum pressure campaign will continue." United Nations Secretary-General António Guterres on Friday expressed his hope that the two countries swiftly implement all agreed actions, including ridding the Peninsula of nuclear arms.

The UN chief "counts on the parties to build on their first meeting and swiftly implement all agreed actions to further inter-Korean trust-building and reconciliation; sincere dialogue; and progress toward sustainable peace and verifiable denuclearization on the Korean Peninsula," Guterres' spokesman Stéphane Dujarric said in a statement.

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