Paris - World leaders and governments hailed the historic summit on Friday between the leaders of North and South Korea as a step towards peace, but also sounded a note of caution about the challenges ahead.North Korean leader Kim Jong Un and South Korean President Moon Jae-In, at the first such summit in 11 years, agreed to pursue a permanent peace and the complete denuclearisation of the divided peninsula.'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," tweeted US President Donald Trump. "Good things are happening, but only time will tell!" added Trump, who is scheduled to meet Kim within weeks.In a second tweet, Trump wrote: "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!"'New journey to stability'"We applaud the Korean leaders' historic step and appreciate their political decisions and courage," Chinese foreign ministry spokeswoman Hua Chunying told a press briefing."We hope and look forward to them taking this opportunity to further open a new journey of long-term stability on the peninsula."She also cited a poem that reads: "We remain brothers after all the vicissitudes; let's forgo our old grudges, smiling we meet again."'Watching North's movements'"Today President Moon Jae-in and Chairman Kim Jong Un held earnest discussions about North Korea's denuclearisation. I want to welcome that as a positive move toward comprehensive resolution of various issues concerning North Korea," Japanese Prime Minister Shinzo Abe told reporters."We strongly hope that North Korea will take concrete action through this meeting and a summit between the US and North Korea."We will keep watching North Korea's future movements."All in all, I wish to continue close coordination between Japan, the United States and South Korea towards comprehensive resolution of the abduction, nuclear and missile issues, and towards the US-North Korea summit talks."'Very positive news'"This is very positive news," Russian President Vladimir Putin's spokesman told reporters."Today we see that this direct dialogue has taken place (and) it has certain prospects," he said."The will to seek agreement can be seen on both sides, including the most important thing - the will to begin and continue dialogue. That is a positive fact," Dmitry Peskov said.'Hard work lies ahead'"This is a first step, it is encouraging, but we have to realise there is still a lot of hard work that lies ahead of us," NATO chief Jens Stoltenberg cautiously said at a meeting of NATO foreign ministers in Brussels.'Truly historic' meetingUN SecretaryGeneral Antonio Guterres welcomed the "truly historic summit" in a statement. Guterres "salutes the courage and leadership that resulted in the important commitments and agreed actions" and counts on the parties to "swiftly implement all agreed actions," the statement added."He looks forward to these gains being consolidated and advanced at the summit between the leaders of the United States and the DPRK expected to take place in the near future," it said, referring to the Democratic People's Republic of Korea, the North's official name.'Against all the odds'EU diplomatic chief Federica Mogherini said the meeting "shows that the way to peace is possible, against all the odds."She said the bloc was ready to lend its "full support to the denuclearisation of the Peninsula.""The European Union, today as always, stands on the side of peace, on the side of de-nuclearisation, and for a prosperous future for all Koreans," she said in a statement. 'Many questions' remaining"I am very encouraged by what's happened. I don't think that anyone looking at the history of North Korea's plans to develop a nuclear weapon will be over-optimistic but it's clearly good news that the two meet," British Foreign Secretary Boris Johnson said in Brussels."This historic summit is not the end in itself. There are still many questions to be answered," he added in a statement.