President Donald Trump on Sunday issued a revised travel ban targeting citizens of eight countries, adding North Korea, Venezuela and Chad to a list of nations the administration says pose a threat to national security.

Restrictions will remain on the majority-Muslim countries of Iran, Libya, Somalia, Syria and Yemen. Sudan was dropped from the list of countries originally targeted by sections of a March 6 executive order that expired Sunday.

The new restrictions go into effect Oct. 18, according to a presidential proclamation issued Sunday night.

The eight countries targeted by the new travel ban are not satisfying new U.S. vetting standards developed by the Homeland Security Department over the past six months, Trump said in the proclamation. He said that, in some cases, the targeted countries are also home to “a significant terrorist presence.”

“I must act to protect the security and interests of the United States and its people,” he said. “I am committed to our ongoing efforts to engage those countries willing to cooperate, improve information-sharing and identity-management protocols and procedures, and address both terrorism-related and public-safety risks.”

The ban affects most travelers from the eight countries, except certain student visa holders from Iran. Lawful permanent residents of the United States, diplomats and refugees are not affected. Some countries face full bans, while others will have tailored restrictions on certain individuals such as government officials.

The enhanced screening standards developed by the DHS are the result of a Trump campaign promise to carry out “extreme vetting” of travelers from countries harboring terrorists. But Trump has been hounded by an earlier call for a “complete and total shutdown of Muslims” entering the U.S. that has driven numerous court challenges to his efforts.

A White House statement said the restrictions on the eight countries are “conditional and may be lifted as they work with the United States Government to ensure the safety of Americans.”

The proclamation comes less than two weeks before the Supreme Court is scheduled to hear oral arguments on the challenges to the legality and constitutionality of the March 6 order.

The move could mean the case fizzles and the justices decline to weigh in at this time, since they would be asked to make a potentially blockbuster ruling on a temporary policy that is no longer in place, legal experts say.

The Justice Department filed a letter with the Supreme Court on Sunday night, suggesting the justices have both sides of the case submit additional briefs in the case “addressing the effects of the Proclamation on the issues currently pending before the Court in these cases.”

Also looming in the case is what happens when the executive order’s temporary ban on refugees entering the country expires on Oct. 24.

Todd Ruger contributed to this report.