Citizens of eight countries will face new restrictions on entry to the United States under a proclamation signed by President Donald Trump on Sunday.

The new rules, which will impact the citizens of Chad, Iran, Libya, North Korea, Somalia, Syria, Venezuela and Yemen, will go into effect on October 18.

The restrictions rage from full travel bans on nationals from countries like Syria to more targeted restrictions. A suspension of non-immigrant visas to citizens for Venezuela, for instance, applies only to senior government officials and their immediate families.

The announcement comes the same day as Trump's temporary ban on visitors from six Muslim-majority countries is set to expire, 90 days after it went into effect. That ban had barred citizens of Iran, Libya, Somalia, Sudan, Syria and Yemen who lack a "credible claim of a bona fide relationship with a person or entity in the United States" from entering the U.S.

"As President, I must act to protect the security and interests of the United States and its people," reads the proclamation.

Officials stressed that valid visas would not be revoked as a result of the proclamation. The order also permits, but does not guarantee, case-by-case waivers.

The restrictions are targeted at countries that Department of Homeland Security officials say refuse to share information with the U.S. or haven't taken necessary security precautions.

"The acting secretary has recommended actions that are tough and that are tailored, including restrictions and enhanced screening for certain countries," said Miles Taylor, counselor to acting Homeland Security Secretary Elaine Duke, said Friday.

Unlike the President's first travel ban, which sparked disorganization at airports across the country and a flurry of legal challenges, officials said they had been working for months on the new rules, in collaboration with various agencies and in conversation with foreign governments.

The restrictions are based on a new baseline developed by DHS that includes factors such as whether countries issue electronic passports with biometric information and share information about travelers' terror-related and criminal histories. The U.S. then shared those benchmarks with every country in the world and gave them 50 days to comply.

The eight countries are those that refused or were unable to comply.

Trump last week called for a "tougher" travel ban after a terrorist attack in the London tube.

"The travel ban into the United States should be far larger, tougher and more specific-but stupidly, that would not be politically correct!" he tweeted.

The President is exercising the authority granted to him by such U.S. Codes as 1182(f) and 1185(a), as well as sections 212(f) and 215(a) of the Immigration and Nationality Act.