The countries affected are Afghanistan, Myanmar, Chad, Congo, Equatorial Guinea, Eritrea, Haiti, Iran, Libya, Somalia, Sudan and Yemen.
The entry of people from seven other countries: Burundi, Cuba, Laos, Sierra Leone, Togo, Turkmenistan and Venezuela, will be partially restricted. The travel restrictions were first reported by CBS News.
"We will not allow people to enter our country who wish to do us harm," Trump said in a video posted on X. He said the list could be revised and new countries could be added.
The proclamation is effective from June 9.
Visas issued before that date will not be revoked, the order said.
During his first term in office, Trump announced a ban on travellers from seven majority-Muslim nations, a policy that went through several iterations before it was upheld by the Supreme Court in 2018.
Former President Joe Biden, who succeeded Trump, repealed the ban in 2021, calling it "a stain on our national conscience."
Trump said the countries subject to the most severe restrictions were determined to harbour a "large-scale presence of terrorists," failed to cooperate on visa security and have an inability to verify travellers' identities, inadequate record-keeping of criminal histories and high rates of visa overstays in the United States.
"We cannot have open migration from any country where we cannot safely and reliably vet and screen those who seek to enter the United States," Trump said.
He cited Sunday's incident in Boulder, Colorado in which a man tossed a petrol bomb into a crowd of pro-Israel demonstrators as an example of why the new restrictions are needed.
An Egyptian national, Mohamed Sabry Soliman, has been charged in the attack. Federal officials said Soliman had overstayed his tourist visa and had an expired work permit - although Egypt is not on the list of countries facing travel limits.
Somalia immediately pledged to work with the US to address security issues.
"Somalia values its longstanding relationship with the United States and stands ready to engage in dialogue to address the concerns raised," Dahir Hassan Abdi, the Somali ambassador to the United States, said in a statement.
Venezuelan Interior Minister Diosdado Cabello, a close ally of President Nicolas Maduro, responded on Wednesday evening by describing the US government as fascist and warning Venezuelans of being in the US
"The truth is being in the United States is a big risk for anybody, not just for Venezuelans ... They persecute our countrymen, our people for no reason."
Trump's directive is part of an immigration crackdown that he launched at the start of his second term.Â
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