Donald Trump has signed two executive orders to ban refugees from entering the US and to rebuild the military.

One order begins the process, in his view, of building up the armed forces, while the other is designed to prohibit radical terrorists from entering the country, but acts as a temporary, blanket ban for any refugee coming to the US.

“This is big stuff,” he said, signing the order in front of a raft of cameras.

It is the first act to institute a threat he first gave in December 2015 shortly after the terrorist attacks in Paris, when he said all Muslims should be banned from the country.

Muslims will be the biggest victim of the new executive order, which was reduced to only target immigrants from seven Muslim-dominated countries: Syria, Iraq, Iran, Libya, Somalia, Sudan and Yemen. No new visas will be issued from these countries for 30 days. These countries are affected by conflict and terrorism, but anyone escaping persecution and death will be barred from refuge in the US.

Syrian refugees will be banned "indefinitely", although an exemption in the order an remarks by Mr Trump indicate Christians from the country will still be allowed in. It already takes around two years for Syrian refugees to be vetted and enter the US.

Refugees from the other six countries will be banned for 120 days.

"[This is a] measure to keep radical Islamic terrorists out of America. We don’t want them here," said Mr Trump.

He warned that the US should never forget the attacks of 9/11 or those who lost their lives in the Pentagon.

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"We don’t want to admit the very threats our soldiers are fighting overseas. We only want to admit those that support our country and love, deeply, our people."

It is yet to be defined how the President will carry out his proposal of "extreme vetting" and the "religious test" of incoming immigrants when the ban is lifted.

Rep Michael McCaul, the Republican and Homeland Security chairman, told CNN that Christians from Syria would not pose a terrorist threat to the US compared to Muslims.

“It seems to be they [Christians] would be top of the list,” he said.

The President has been widely condemned for threatening to institute this order, which was seen as discriminatory.

It was signed on International Holocaust Remembrance Day, a reminder that the US barred tens of thousands of Jews from a safe haven when more than six million of their people were being murdered by Nazis.

He then signed another executive order to rebuild the military, to build “new planes, new ships, tools and resources”.

In 2015, the US spent $598 billion on the military.

"As we prepare our budget request for Congress, our military strength will be questioned by no one and neither will our dedication to peace. And we do want peace," he said.

The orders were signed while General James Mattis was being sworn in as defense secretary.