Reiterating his doubts that Russia was behind cyber meddling in the US elections, President-elect Donald Trump said that he knew "things that other people don't know" about the hacking, and that the information would be revealed "on Tuesday or Wednesday".

Speaking to reporters outside his Mar-a-Lago estate in Florida, Trump cast his declarations of doubt as an effort to seek the truth, the New York Times reported on Saturday.

"I just want them to be sure because it's a pretty serious charge," Trump said of the intelligence agencies. 

"If you look at the weapons of mass destruction, that was a disaster, and they were wrong," he added, referring to intelligence cited by the George W. Bush administration to support its march to Iraq war in 2003. 

"So, I want them to be sure," the President-elect said. "I think it's unfair if they don't know."

He added: "And I know a lot about hacking. And hacking is a very hard thing to prove. So, it could be somebody else. And I also know things that other people don't know, and so they cannot be sure of the situation."

When asked what he knew that others did not, Trump said, "You'll find out on Tuesday or Wednesday."

Trump, who does not use email, also advised people to avoid computers when dealing with delicate material. 

"It's very important, if you have something really important, write it out and have it delivered by courier, the old-fashioned way, because I'll tell you what, no computer is safe," Trump said.

The comments on Saturday were a departure from a statement that Trump issued through transition officials last week, in which he said that it was time for people to "move on" from the hacking issue but that he would be briefed on the matter by intelligence officials early in the New Year.