US President Donald Trump has signed a revised travel ban that will temporarily halt entry to the US for people from six Muslim-majority nations.

Under the order announced on Monday, a 90-day ban on travel to the US will be imposed on citizens of Iran, Libya, Syria, Somalia, Sudan and Yemen.

Unlike the previous ban, the new directive does not include Iraq in its list of countries targeted, following pressure from the Pentagon and State Department, which had urged the White House to reconsider, given Iraq's key role in fighting the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) group.

Travellers holding pre-existing visas would still be allowed entry, according to the new order.

US Secretary of State Rex Tillerson declared that the renewed ban is "a vital measure for strengthening our national security".

"With this order, president Trump is exercising his rightful authority to keep our people safe," Tillerson said.

White House spokesperson Sarah Huckabee Sanders had said earlier on Monday that the new order would take effect on March 16.

The first order, signed on January 27, led to chaos at airports, protests and international condemnation. That order was ultimately blocked by the courts .