The Trump administration on Tuesday said it paused all immigration applications, including green card and U.S. citizenship processing, filed by immigrants from 19 non-European countries, citing concerns over national security and public safety.

The pause applies to people from 19 countries that were already subjected to a partial travel ban in June, placing further restrictions on immigration - a core feature of U.S. President Donald Trump's political platform.

The list of countries includes Afghanistan and Somalia.

The official memorandum outlining the new policy cites the attack on U.S. National Guard members in Washington last week, in which an Afghan man has been arrested as a suspect. One member of the National Guard was killed, and another was critically wounded in the shooting.

Trump has also stepped up his rhetoric against Somalis in recent days, calling them “garbage” and saying “we don’t want them in our country.”

Since returning to the office in January, Trump has aggressively prioritised immigration enforcement, sending federal agents to major U.S. cities and turning away asylum seekers at the U.S.-Mexico border. His administration has frequently highlighted the deportation push, but until now it has put less emphasis on efforts to reshape legal immigration.

The flurry of promised restrictions since the attack on National Guard members suggests an increased focus on legal immigration framed around protecting national security and casting blame on former President Joe Biden for his policies.

The list of countries targeted in Wednesday's memorandum includes Afghanistan, Burma, Chad, the Republic of the Congo, Equatorial Guinea, Eritrea, Haiti, Iran, Libya, Somalia, Sudan and Yemen, which were subjected to the most severe immigration restrictions in June, including a full suspension on entries with a few exceptions.

Others on the list of 19 countries, which were subjected to partial restrictions in June, are Burundi, Cuba, Laos, Sierra Leone, Togo, Turkmenistan and Venezuela.

The new policy places a hold on pending applications and mandates that all immigrants from the list of countries "undergo a thorough re-review process, including a potential interview and, if necessary, a re-interview, to fully assess all national security and public safety threats."

The memorandum cited several recent crimes suspected to have been committed by immigrants, including the National Guard attack.

Sharvari Dalal-Dheini, senior director of government relations for the American Immigration Lawyers Association, said the organisation had received reports of cancelled oath ceremonies, naturalisation interviews and adjustment of status interviews for individuals from countries listed on the travel ban.