Donald Trump has a query: Why can't US use nukes?

Washington: US Republican presidential nominee Donald Trump is reported to have asked why the United States can't use nuclear weapons!

He posed the question before a foreign policy expert who has been advising him.

The revelation was made by MSNBC's Joe Scarborough Wednesday on his "Morning Joe" program.

The TV host based his claim on an unnamed source who said he had spoken with Trump.

"Several months ago, a foreign policy expert on the international level went to advise Donald Trump. And three times (Trump) asked about the use of nuclear weapons. Three times he asked at one point if we had them why can't we use them," Scarborough said on the show.

Scarborough made the revelation while interviewing former Director of Central Intelligence and ex-National Security Agency Director Michael Hayden.

The Trump campaign has rejected the claims.

Outgoing President Barack Obama has already described Trump as "unfit to serve as President".

Democratic presidential nominee Hillary Clinton, too has said that Trump can't be trusted with nukes.

"A man you can bait with a tweet is not a man we can trust with nuclear weapons," she has said.