US president-elect Donald Trump pointed to remarks by WikiLeaks founder Julian Assange on the hacking of Democratic Party emails as he questioned US intelligence agencies' assessment that Russian hackers were behind the breach

"Julian Assange said 'a 14-year-old could have hacked Podesta' - why was DNC so careless? Also said Russians did not give him the info!" Trump wrote on Twitter on Wednesday, referring to the Democratic national committee, the party's formal governing body.

He said earlier a briefing on the hacking had been "delayed until today, perhaps more time needed to build a case. Very strange!"

The White House said Trump's characterization of the briefing's timing was inaccurate, and questioned his pointing to Assange.

"The real question that looms is a question that's been raised by some of the public comments or tweets from the president- elect which is just simply, who are you going to believe?" White House spokesperson Josh Earnest asked.

"On one hand you've got the Russians and the aforementioned Mr Assange. On the other side, you've got the 17 intelligence agencies of the United States government, outside cyber experts that have taken a look at this situation."

'Could have been 14-year-old'

Obama last week expelled Russian diplomats and ordered new sanctions over the hacking that he says was an attempt to interfere in the US presidential elections.

Trump has been sceptical of US intelligence claims, and vice president-elect Mike Pence on Wednesday pointed to past intelligence failures.

In an interview with Fox News, Assange said Hillary Clinton's campaign chairperson John Podesta had opened himself up to the hacking through a phishing expedition that could have been carried out by a "14-year-old kid".

WikiLeaks published a series of emails during the presidential election from the DNC and Podesta's private email that were seen as damaging to Clinton's campaign against Trump.

Assange denied that WikiLeaks received the emails from the Russian government and dismissed the US intelligence assessment.

Trump's remarks also drew criticism from some members of his Republican Party, with senator Lindsey Graham stressing Assange's lack of crediblity and desire to harm the United States.

He dismissed efforts to pin the hacking on someone besides Russian agents.

"It wasn't a 14-year-old kid, unless he was working for the KGB. It wasn't a 300-pound guy unless he was a Russian agent," he said.

Trump himself had once called WikiLeaks "disgraceful" and called in a 2010 Fox News interview for the "death penalty" for its role in publishing classified US information.

McCain: 'Correct so far'

US Senator John McCain meanwhile said he hopes president-elect Donald Trump can understand the role of the intelligence community.

McCain says it's clear that their conclusions about Russian cyberattacks "have been correct so far" and their work should be respected.

He says US intelligence agencies may have made some mistakes in the past, but they still are "vital" in providing counsel for the defence and security of the United States.

McCain made the comments after a hearing on Capitol Hill about Russian-directed hacking and other cyberactivities during the US presidential election.

- dpa