WASHINGTON — President Donald Trump has signed a proclamation imposing strict new restrictions on travellers from a handful of countries, including five that were covered by his expiring travel ban. Administration officials say the new measures are required to keep the nation safe.

The indefinite restrictions apply to citizens of Chad, Iran, Libya, Somalia, Syria, Yemen and North Korea. As part of the presidential proclamation signed Sunday, the U.S. will also bar the entry of certain Venezuelan government officials and their immediate families.

The changes will take effect October 18.

The announcement came the same day that Trump’s temporary ban on visitors from six Muslim-majority countries was set to expire, 90 days after it went into effect. That ban had barred citizens of Iran, Libya, Somalia, Sudan, Syria and Yemen who lacked a “credible claim of a bona fide relationship with a person or entity in the United States” from entering the U.S. Only one of those countries, Sudan, will no longer be subject to travel restrictions.

“Making America Safe is my number one priority. We will not admit those into our country we cannot safely vet,” Trump tweeted late Sunday after the new policy was announced.

Unlike the first iteration of Trump’s travel ban, which sparked chaos at airports across the country and a flurry of legal challenges after being hastily written with little input outside the White House, officials stressed they had been working for months on the new rules, in collaboration with various agencies and in conversation with foreign governments.

To limit confusion, valid visas would not be revoked as a result of the proclamation. The order also permits, but does not guarantee, case-by-case waivers for citizens of the affected countries.

The restrictions are targeted at countries that the Department of Homeland Security says fail to share sufficient information with the U.S. or haven’t taken necessary security precautions.

DHS has spent recent months working to develop a new security baseline, which includes factors such as whether countries issue electronic passports with biometric information, report lost or stolen passports to INTERPOL, an international law enforcement body, and share information about travellers’ terror-related and criminal histories.

Citizens of countries that don’t meet the standard will face restrictions until they make changes to bring them into compliance.

The new rules include the suspension of all immigrant visas for nationals of Chad, Iran, Libya, North Korea, Syria, Yemen and Somalia, and the suspension of non-immigrant visas, such as for business and tourism, to nationals of Chad, Libya, North Korea, Syria and Yemen.

Citizens of Iran will not be eligible for tourism and business visas, but remain eligible for student and cultural exchange visas if they undergo additional scrutiny. Such additional scrutiny will also be required for Somali citizens applying for all non-immigrant visas.

Critics have accused Trump of overstepping his legal authority and violating the U.S. Constitution’s protections against religious bias each time he has ordered new travel restrictions.

And the inclusion of Venezuela and North Korea appeared to be an attempt to block challenges from advocacy groups and others who have called the restrictions a ban on Muslims. Trump during his campaign called for a “total and complete shutdown of Muslims entering the United States.”

The U.S. had already imposed wide-ranging sanctions on certain high-ranking Venezuelan government officials to protest the government’s attempts to consolidate power.

“The fact that Trump has added North Korea – with few visitors to the U.S. – and a few government officials from Venezuela doesn’t obfuscate the real fact that the administration’s order is still a Muslim ban,” said Anthony D. Romero, executive director of the American Civil Liberties Union, which has been challenging the ban in court. “President Trump’s original sin of targeting Muslims cannot be cured by throwing other countries onto his enemies list.”

But administration officials argue the measure is necessary to keep Americans safe.