Additionally, Mr Trump's order suspends the entire US refugee programme for 120 days, although refugees already formally scheduled for travel by the State Department will be allowed entry. When the suspension is lifted, the number of refugees allowed into the US will be capped at 50,000 for the fiscal year 2017.

Other changes are also expected, including no longer singling out Syrian refugees for an indefinite ban. Syrian refugees will now be treated like other refugees and be subject to the 120-day suspension of the refugee programme.

The new version of the order is also expected to remove language that would give priority to religious minorities. Critics had accused the administration of adding such language to help Christians get into the United States while excluding Muslims.

"I think people will see six or seven major points about this executive order that do clarify who was covered," Kellyanne Conway, the presidential counselor, said in an interview with Fox News Channel's "Fox & Friends."

She said the new order will not go into effect until March 16, despite earlier warnings from the president and his team that any delay in implementation would pose a national security risk, allowing dangerous people to flow into the country.

Legal experts say the new order addresses some of the constitutional concerns raised by a federal appeals court about the initial ban, but leaves room for more legal challenges.