WASHINGTON (Reuters) - U.S. green card holders from Syria and six other Muslim-majority countries traveling outside the United States need to check with a U.S. consulate to see whether they can return, senior U.S. administration officials said on Saturday.

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New restrictions on immigrants and refugees in an executive order signed by President Donald Trump will mean legal permanent residents who have passports from the seven countries have to be cleared back into the United States on a case-by-case basis, an official told reporters in a briefing.

“It’s being cleared on a case-by-case basis and being moved expeditiously,” the official said.

The official defended the scope and execution of the new rules, saying it moved with “astonishing rapidity” but worked as intended.

Confusion abounded at airports as immigration and customs officials struggled to interpret the new rules, with some legal residents who were in the air when the order was issued detained at airports upon arrival.

The ban affects travelers with passports from Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen.

The official argued the pause on travel from the countries is a response to concerns that immigration and refugee programs are being abused. The Trump administration is developing stricter rules for vetting people who want to come to the United States.

Immigration lawyers, human rights groups and some U.S. senators have sharply criticized the order, which already faces legal challenges.

The executive order also seeks to prioritize refugees fleeing religious persecution, a move Trump separately said was aimed at helping Christians in Syria, leading some legal experts to question whether the order was constitutional.

Asked about lawsuits, the official said foreigners do not have a right to enter the United States, and dismissed as “ludicrous” critics’ claims that the order is directed at Muslims.

Afghanistan, Malaysia, Pakistan, Oman, Tunisia and Turkey were Muslim-majority countries not included in the order, a second official said.