He said he was forced to make a false confession.
"We have been deceived by the United States."
Kim's birthday is believed to be January 8, though his secretive regime has never confirmed the date.
"He did sign a contract, he did sign an agreement talking about denuclearisation."
It'll be unveiled "in the near future", dictator Kim Jong-un said.
The White House has vowed to take appropriate action in response.
North Korea has threatened the US with an unwanted "Christmas gift".
North Korean leader Kim Jong-un and US President Donald Trump have met three times since June 2018.
Washington's "malicious words" would only aggravate tensions, the hermit state said.