After the president’s first travel ban attempt, introduced via an executive order in January, was knocked down in the US courts and caused travel chaos, Monday’s new order targets just six mostly Muslim nations and will not take effect until March 16.

Iraq has been omitted.

The 90-day ban includes ramped up screening and is aimed at the issuing of new visas to citizens from Syria, Yemen, Libya, Iran, Somalia and Sudan.

Refugees on Manus Island and Nauru that could be part of the Australian-US refugee deal include citizens of three targeted nations: Iran, Somalia and Sudan.

“This executive order seeks to protect the American people as well as lawful immigrants by putting in place an enhanced screening and vetting process for visitors from six countries,” US Attorney-General Jeff Sessions told reporters.

“Three of these nations are state sponsors of terrorism.

“The other three have served as safe havens for terrorists.”

Under the new order, the US will also suspend its refugee program for 120 days and cut the number of refugees its accepts from 110,000, a cap set when Barack Obama was president, to 50,000.

Trump has already called the Australian-US refugee agreement a “dumb deal”.

The new order is aimed at blocking potential terrorists entering the US.

Sessions said the FBI was investigating more than 300 people who came to the US as refugees for terrorism related activities.

“As president Trump noted in his address to Congress the majority of people convicted in our courts for terrorism related offences since 9/11 came here from abroad,” Sessions said.

“We also know many people seeking to support or commit terrorist attacks will try to enter through our refugee program.

“In fact, today more than 300 people, according to the FBI, who came here as refugees are under FBI investigation today for potential terrorism related activities.

“Like every nation, the United States has a right to control who enters our country and to keep out those who would do us harm.”

US Secretary of State Rex Tillerson issued a plea to allies for understanding.

“To our allies and partners around the world, please understand this order is part of our ongoing efforts to eliminate vulnerabilities that radical Islamist terrorists can and will exploit for destructive ends,” Tillerson told reporters.

“The State Department will coordinate with other federal agencies and implement these temporary restrictions in an orderly manner.

“Our embassies and consulates around the world will play an important role in making sure that our nation is as secure as it can be and the State Department will implement the provisions in this order that allow for the admissions of refugees when it is determined they do not pose a risk to the security or welfare of the United States.”

Trump has made the signing of executive orders media events, but on Monday the press was not invited to the signing.

Sessions, Tillerson and Homeland Security Secretary John Kelly spoke at a travel ban media event in Washington DC, but declined to answer reporter’s questions.

The silence came after a week of controversy for Trump, with the president using Twitter to accuse Obama of wire tapping his phones and Sessions announcing he would recuse himself from investigations into links between Russia and Trump’s 2016 election campaign.

– AAP