No one replied, but South Korean officials realized the working day may not have begun as North Korean time has run 30 minutes behind Seoul since Pyongyang created a different time zone in August 2015.
In a New Year's Day speech, North Korean leader Kim Jong Un declared that Pyongyang possessed weapons capable of striking the mainland USA and insisted that the world would have to accept his country as a nuclear-armed state.
On Thursday, the US and South Korea announced that they would delay annual joint military exercises ahead of the Winter Olympics. South Korea and the United States are technically still at war with North Korea after the 1950-53 Korean conflict ended with a truce, not a peace treaty.
"With all of the failed "experts" weighing in, does anybody really believe that talks and dialogue would be going on between North and South Korea right now if I wasn't firm, strong and willing to commit our total "might" against the North. Fools, but talks are a good thing!" he said on Twitter.
China, meanwhile, announced that it was tightening restrictions on trade with North Korea under United Nations nuclear sanctions, imposing a cap on oil supplies to the North and banning imports of its steel and other goods.
A visitor takes picture in front of ribbons wishing for the reunification of the two Koreas..
South Korea said Friday that both Koreas had agreed to hold their first talks in more than two years on Tuesday.
The announcement came hours after the United States said it had agreed to delay joint military exercises with South Korea until after the Winter Olympics.
The development comes amid signs of a thaw between North and South despite tensions that have soared between the two - as well as between Washington and Pyongyang - during recent months over the North's ongoing nuclear weapons and missile tests.
The Commerce Ministry said Beijing would limit exports of crude oil and refined petroleum to the North and ban outright sales of steel and industrial machinery.
Earlier this week, Nikki Haley, the US ambassador to the United Nations, said Washington had heard reports that Pyongyang might be preparing to fire another missile.