Despite increasing tensions between North Korea and the United States and its allies in 2017, the North’s leader, Kim Jong Un, reopened a hotline with South Korea that has gone unused for roughly two years in a move that CNN has called a “major diplomatic breakthrough.”

Although all the two countries did after establishing contact was ensure that the cross-border hotline was still working, the move was still a sign of improving relations between them. It comes shortly after the Northern dictator announced on New Year’s Day that 2018 was an important year for both nations; his country is marking its 70th anniversary and the is South hosting the Winter Olympic Games in Pyeongchang. Kim also expressed interest in holding talks with the South about sending athletes to those games.

Some feel that Kim’s recent conciliatory attitude towards the South is meant to distance the South from the United States, which, under President Trump, has been increasingly hostile to North Korea.

In an especially inflammatory tweet, the President mocked North Korea’s nuclear capabilities, remarking, “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!”

Although the reopening of the hotline and Kim Jong Un’s unusually friendly speech suggest the North is calming down its rhetoric, it should be noted that, as the President referenced in the above tweet, Kim, in the same speech, threatened the United States by saying he now has a red button on his desk controlling his country’s nuclear arsenal. While the country completed a concerning number of nuclear tests last year, the extent of its nuclear capability, perhaps most critically its ability to launch a warhead across the Pacific and strike the United States, is currently unknown.