Donald Trump announces James Mattis as defence secretary

US President-elect Donald Trump has selected the retired marine general James Mattis to serve as his first Pentagon chief, the first of his national-security appointments.

Trump made the announcement at an Ohio rally on the first day for his “thank you tour”.

Mattis, known as "Mad Dog" and renowned for his tough talk and battlefield experience in Iraq and Afghanistan, was an outspoken critic of the Obama administration's Middle East policy, particularly on Iran.

"We are going to appoint 'Mad Dog' Mattis as our secretary of defense," Trump told a rally in Cincinnati. He said the formal announcement would be made on Monday.

Because Mattis retired only in 2013, Reuters news agency reported that he would need the US Congress to waive a requirement that a defence secretary be a civilian for at least seven years before taking the top job at the Pentagon. His impressive combat record, however, may deter some Senate Democrats from trying to block his nomination, it said.