Donald Trump has signalled that retired general James Mattis is a likely pick for the top job of defence secretary.

Mr Trump called him "James Mad Dog Mattis" and told reporters he was "the real deal", tweeting praise about the retired general after an hour-long meeting on Saturday.

Mr Mattis served 44 years, rising through the ranks of Marine Corps, and led a task force into southern Afghanistan in 2001 as well as a Marine division during the Iraq invasion in 2003.

The four-star general was praised for leading Marines in the 2004 battle of Falluja in Iraq, described as one of the bloodiest of the war.

The following year, however, he was condemned for saying "it’s fun to shoot some people" while talking to service members in San Diego.

"Actually it's quite fun to fight them, you know. It's a hell of a hoot," he said during the panel discussion. "It's fun to shoot some people. I'll be right up there with you. I like brawling.

"You go into Afghanistan, you got guys who slap women around for five years because they didn't wear a veil. You know, guys like that ain't got no manhood left anyway. So it's a hell of a lot of fun to shoot them."

Obama: I'll weigh in on Trump's presidency if necessary

He was promoted to run the US Central Command in 2010, responsible for all US forces in the Middle East. Like Mr Trump, he is a critic of president Obama’s nuclear deal with Iran.

He would need a waiver from congress to be eligible for the top job, however, as he would normally be required to be out of uniform for at least seven years before taking on the Pentagon responsibility.

Vice president-elect Mike Pence told Fox News that Mr Mattis had a "legendary military career".

Mr Trump has now selected Alabama senator Jeff Sessions to run the justice department, retired army lieutenant general Michael Flynn as national security adviser and US representative Mike Pompeo as CIA chief.

Mr Sessions has been criticised for his litany of past racist comments and Mr Flynn has called Islam a "cancer".