President Trump expressed cautious optimism about the historic meeting between North Korean Leader Kim Jong Un and South Korean President Moon Jae-in, as U.S. officials plan their own meeting with the North Korean leader over his nuclear missile program.

Kim and Moon met for the first time this week, with images and videos overnight emerging to show seemingly cordial interactions between the two as they signed a declaration on Friday establishing a goal of "no more war" and "complete denuclearization" of the Korean peninsula. Meanwhile, the White House intends for a meeting with North Korea to take place in the weeks ahead, as the U.S. seeks total denuclearization of the North.

"After a furious year of missile launches and nuclear testing, a historic meeting between North and South Korea is now taking place," Mr. Trump tweeted early Friday morning. "Good things are happening, but only time will tell!"

After a furious year of missile launches and Nuclear testing, a historic meeting between North and South Korea is now taking place. Good things are happening, but only time will tell! — Donald J. Trump (@realDonaldTrump) April 27, 2018

Mr. Trump followed up in another tweet Friday, saying, "KOREAN WAR TO END! The United States, and all of its GREAT people, should be very proud of what is now taking place in Korea!"

KOREAN WAR TO END! The United States, and all of its GREAT people, should be very proud of what is now taking place in Korea! — Donald J. Trump (@realDonaldTrump) April 27, 2018

Mr. Trump also gave some credit to Chinese President Xi Jin Ping for progress with North Korea, even as he has sparred with China over trade and tariffs.

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! — Donald J. Trump (@realDonaldTrump) April 27, 2018

Mr. Trump has expressed interest in talks with North Korea before, but has also said he will cancel the intended meeting if he isn't satisfied with the way things are going, and will "leave" the summit if it isn't successful. Newly confirmed Secretary of State Mike Pompeo traveled to North Korea and met with Kim over Easter weekend, a precursor to the intended U.S.-North Korea summit. The Trump administration has yet to announce an exact date or location for such a meeting.

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Key in that meeting will be what agreement North Korea and the U.S. can reach on denuclearization. Mr. Trump has defined denuclearization as, "It means they get rid of their nukes, very simple."