President-elect Donald Trump is warning that he knows "things other people don't know" about claims that the Russian government was behind the hacking of political groups during the U.S. presidential election, and is promising to spill the beans "Tuesday or Wednesday."

Trump, who has refused to acknowledge U.S. intelligence assessments that determined the hacking was directed by the highest levels in the Russian government, said he's been skeptical because he wants U.S. intelligence officials to be 100 percent sure.

"I just want them to be sure because it's a pretty serious charge," Trump told reporters in an impromptu New Year's Eve press conference.

"If you look at weapons of mass destruction, it was a disaster, and they were wrong," he said. "So I want them to be sure. I think it's unfortunate if they don't know. I know a lot about hacking, and hacking is a very hard thing to prove. So it could be somebody else."

"I also know things other people don't know," Trump added. "So they cannot be sure of this situation."

When a reporter asked Trump what he knew about the hacking situation, Trump said: "You'll find out Tuesday or Wednesday," with no explanation for the delay. His comments were made at Trump's Palm Beach estate.

The president-elect has said he plans to meet with intelligence officials in coming days to learn more about the allegations.

Trump, who says "no computer is safe" when it comes to keeping information private, said, "if you have something really important, write it out and have it delivered by courier, the old-fashioned way."

President Obama ordered sanctions on Russian spy agencies last week, closed two Russian compounds and expelled 35 diplomats the U.S. said were really spies. The Russian government has denied the allegations.

(c)2017 the Boston Herald