Russia's Vladimir Putin bigger threat than ISIS: US senator

Sydney: Russian President Vladimir Putin is a bigger threat to world security than the so-called ISIS group, according to veteran US Senator John McCain who also admits Donald Trump makes him "nervous".

Republican McCain -- one of US President Trump's most outspoken critics in his own party -- said Russia's alleged meddling in elections was a danger to democracy.

"I think he (Putin) is the premier and most important threat, more so than ISIS," McCain, chairman of the Senate Armed Services Committee, told the Australian Broadcasting Corporation late Monday.

"I think ISIS can do terrible things ... but it is the Russians who are trying, who tried to destroy the very fundamental of democracy and that is to change the outcome of an American election.

"I have seen no evidence they succeeded but they tried and they are still trying. They just tried to affect the outcome of the French election.

"So I view Vladimir Putin, who has dismembered the Ukraine, a sovereign nation, who is putting pressure on the Baltics, I view the Russians as the far greatest challenge that we have."

McCain's comments come with the Trump team embroiled in controversy over its relationship with Moscow, which US intelligence agencies say tried to sway last November's election in the property tycoon's favour.

A broad investigation into Russia's apparent meddling is being led by Robert Mueller, a respected former FBI director who was given wide powers to pursue the case as a special counsel.

The US Senate and House Intelligence committees are also leading their own probes.

Over the weekend the furore pierced the innermost circle of the White House with reports that Trump's son-in-law Jared Kushner sought a secret communications link to Russia -- an allegation the president called "fabricated."

Asked about the Kushner revelation, McCain, in Australia on a visit, said: "My view of it is I don't like it.

"I know that some administration officials are saying 'well that's standard procedure'.

"I don't think that it's standard procedure prior to the inauguration of a president of the United States by someone who is not in an appointed position."

When put to him by the ABC that some people feel nervous about international security with Trump as president, McCain said he understood why.

"I am nervous from time to time," he said. "I do believe that the president has great confidence in the national security team. I do believe most of the time that he accepts their advice and counsel.

"Can I tell you that he does (that) all the time? No. Does it bother me? Yes, it bothers me."