Washington DC - The US government has halted immigration applications for citizens from 19 nations including Afghanistan, Yemen, and Haiti, said an official memorandum released on Tuesday.

Authorities paused green card and citizenship processing, according to the memo, for people from countries already subject to travel restrictions announced by President Donald Trump in June.

Those 19 nations also include Venezuela, Sudan, and Somalia.

Senior US officials have signaled in recent days they would starkly tighten restrictions on immigration, fueled by the shooting of two National Guard soldiers last week.

The main suspect in the shooting, which killed one, is an Afghan national. The man, who on Tuesday pled not guilty to murder charges, entered the US during mass evacuations as foreign forces withdrew from Afghanistan in 2021.

"USCIS plays an instrumental role in preventing terrorists from seeking safe haven in the United States and ensuring that USCIS' screening and vetting and adjudications prioritize the safety of the American people and uphold all US laws," the memorandum said, referring to the US Citizenship and Immigration Services.

The memorandum said that the US has recently seen "what a lack of screening, vetting, and prioritizing expedient adjudications can do to the American people," citing the suspected shooter in last week's attack as an example.