As reported by Democracy Now!:
In North Korea, leader Kim Jong-un has ordered the reopening of a hotline with South Korea’s leaders—bringing the biggest thaw in relations between the two Koreas in years. The overture came as South Korean President Moon Jae-in said he’s open to talks next week in the so-called truce village in the Demilitarized Zone. The moves came as President Trump took to social media to make a threat of nuclear war steeped in sexual bravado. Trump tweeted from the White House, “North Korean Leader Kim Jong Un just stated that the 'Nuclear Button is on his desk at all times.' Will someone from his depleted and food starved regime please inform him that I too have a Nuclear Button, but it is a much bigger & more powerful one than his, and my Button works!” Trump’s tweet was among a torrent of 16 messages he posted to Twitter on his first full day of work in the new year, with attacks on Pakistan, the Palestinians, Hillary Clinton, Huma Abedin, James Comey and The New York Times. (emphasis added)
New York Times coverage also commented along similar lines:
The president’s tone also generated a mix of scorn and alarm among lawmakers, diplomats and national security experts who called it juvenile and frightening for a president handling a foreign policy challenge with world-wrecking consequences. The language was reminiscent of Mr. Trump’s boast during the 2016 presidential campaign that his hands, and by extension his genitals, were in fact big enough.
The Washington Post's James Hohmann has taken an even deeper dive on Trump's fixation on size.