North Korea called South Korea on Wednesday on a hotline that had previously remained dormant for two years, in a major diplomatic breakthrough that could pave the way towards future peace talks.

Pyongyang’s state-run TV station reported on Wednesday morning that the inter-Korean communications channel in the shared border village of Panmunjom would be opened at 3pm local time [6:30 am GMT].

This was confirmed by South Korea’s unification ministry who said that the North made contact via the phone line at exactly the time ordered. “We have checked the communication line and are contacting each other,” it said.

The breakthrough came despite an astonishing tweet late on Tuesday by US President Donald Trump, boasting that his “nuclear button” was bigger than North Korean dictator Kim Jong-un’s.

“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!” he wrote, to an aghast Twitter audience.

Kim’s olive branch to the South followed a New Year’s Day speech in which he said he was “open to dialogue” with Seoul and to sending a team to South Korea’s Pyeongchang Winter Olympic Game in February.