The memo said USCIS “plays an instrumental role in preventing terrorists from seeking safe haven in the United States”.
The country had recently seen “what a lack of screening, vetting, and prioritising expedient adjudications can do to the American people”, it added, citing the Afghan murder suspect.
Some immigration law experts said the document had plunged many people into limbo.
“Even people who fully passed the citizenship exam are having their cases put on hold, just inches from the finish line,” said Aaron Reichlin-Melnick, a senior fellow at the American Immigration Council, in a post on X.
Those whose applications have already been processed could also face more scrutiny, with the memo vowing a “comprehensive re-review” of nationals from the 19 countries who came to the United States after January 20, 2021.
Trump, who campaigned for the White House on a pledge to deport millions of undocumented migrants, said following the shooting that he planned to “permanently pause migration from all Third World Countries to allow the US system to fully recover”.
Homeland Security chief Kristi Noem said Monday she would push to expand the list of restricted countries.
“I just met with the President. I am recommending a full travel ban on every damn country that’s been flooding our nation with killers, leeches, and entitlement junkies,” she said on X, without naming which countries should be included.
The travel restrictions currently also apply to Burundi, Chad, the Republic of Congo, Cuba, Equatorial Guinea, Eritrea, Iran, Laos, Libya, Myanmar, Sierra Leone, Togo, and Turkmenistan.
US media reported on Tuesday that federal authorities planned to launch a major immigration enforcement operation against Somali immigrants in Minnesota in the coming days, sparking pushback from local leaders who said state police would not co-operate.
“Our values and our commitments to the Somali community, to every community of immigrants and people in our city is rock solid and will be unwavering,” said Minneapolis mayor Jacob Frey.
-Agence France-Presse