Washington - US President Donald Trump agreed on Thursday to a historic first meeting with Kim Jong Un in a stunning development in America's high-stakes nuclear standoff with North Korea.Standing in front of the White House, South Korean National Security Advisor Chung Eui-yong earlier announced the first ever meeting between a US president and North Korean leader, which he said would take place by the end of May.Chung had recently returned from Pyongyang, where he met Kim personally. According to the South Korean official, the reclusive young leader "expressed his eagerness to meet president Trump as soon as possible".Trump confirmed he had agreed to meet Kim - hailing "great progress" in the push to persuade Pyongyang to end its nuclear programme."Meeting being planned!" Trump tweeted. "Kim Jong Un talked about denuclearization with the South Korean Representatives, not just a freeze. Also, no missile testing by North Korea during this period of time."Great progress being made but sanctions will remain until an agreement is reached."Nuclear standoffThe news came almost out of the blue, after a period of extreme tension and bellicose rhetoric between Washington and Pyongyang that sounded like the growing drumbeat of war.Just months ago, Trump mocked Kim by calling him "little rocket man" and Kim returned the favour by describing Trump as "mentally deranged" and a "dotard".The United States and North Korea were foes throughout the Cold War and fought on the opposite side of a bloody war in the 1950s.In the last two decades, they have been engaged in what is perhaps the world's most dangerous nuclear standoff, with 30 000 US military personnel stationed just over the border in the South.Pyongyang's recent race to develop a nuclear weapon capable of hitting the continental United States prompted Trump to embark on a campaign of sanctions, diplomatic pressure and the threat of military force.The White House said that strategy of "maximum pressure" would stay in place, for now."We look forward to the denuclearisation of North Korea. In the meantime, all sanctions and maximum pressure must remain."Paradigm shiftBut the prospect of a top-level meeting is nothing short of a paradigm shift.North Korean leaders have sought face-to-face talks with consecutive US presidents, who have rebuffed the notion as an effort to achieve strategic parity that does not exist.Pyongyang now seems to have achieved its goal, while only agreeing to a temporary suspension of nuclear tests.It is a gambit fraught with risk for Trump. On multiple occasions, Kim's father Kim Jong Il dangled the prospect of talks and denuclearisation as a means of buying time, easing sanctions and dividing South Korea from its allies.However his decision also carries historic echoes of Richard Nixon's visit to communist China or Barack Obama's overture to Cuba, both of which offered the hope of better ties. Kim Jong Un talked about denuclearization with the South Korean Representatives, not just a freeze. Also, no missile testing by North Korea during this period of time. Great progress being made but sanctions will remain until an agreement is reached. Meeting being planned!— Donald J. Trump (@realDonaldTrump) March 9, 2018 The table was set for the announcement on Tuesday when South Korea shocked the world by announcing that the North had stated there was "no reason" to hold on to its nuclear weapons "if military threats towards the North are cleared and the security of its regime is guaranteed".The North is open to "frank" talks with the United States on denuclearisation and would suspend missile and nuclear tests while dialogue was under way, Chung said after returning from a meeting in Pyongyang.Seoul also announced the two Koreas would hold a historic summit in the Demilitarised Zone next month - and that the North's leader Kim Jong Un was ready to halt provocative missile and nuclear tests and sit down with its old enemies.Trump had welcomed the offer as "very positive" and refused to rule out a meeting with Kim. "We have come a long way at least rhetorically with North Korea," Trump said.Opening or trap? However his Director of National Intelligence Dan Coats told Congress he was "quite sceptical" and US Vice President Mike Pence said the US position towards North Korea would not change "until we see credible, verifiable, and concrete steps toward denuclearisation".In the past North Korea has indicated that security guarantees mean US forces leave the Korean peninsula and break a mutual defence treaty with the South.Although Trump's response was positive, his administration followed it up with another sharp rebuke when it declared that it had formally concluded Kim's regime had last year murdered his half-brother in a Malaysian airport with the banned VX nerve agent.Trump also sounded a note of warning, signalling the threat of military action remains on the table should talks fail to make headway, and his administration said it would press ahead with potentially provocative joint war games with South Korea.The United States says Pyongyang is testing - and will soon complete - an intercontinental ballistic missile capable of delivering a nuke to the continental United States.That ominous technological breakthrough would put cities like Los Angeles and even New York in striking distance of a hostile regime, something that is unthinkable to many in the West Wing.