Dec. 3 (UPI) -- The Trump administration on Tuesday announced a pause on immigration application processing for nationals from 19 countries and said it would re-examine immigration and asylum cases approved during the Biden administration.

The U.S. Citizenship and Immigration Services announced the hold and review of all pending asylum applications and USCIS benefits applications filed by immigrants from the so-called high-risk countries in a four-page memo on Tuesday.

"USCIS has determined the operational necessity to ensure that all asylum applicants and aliens from high-risk countries of concern who entered the United States do not pose a threat to national security or public safety," the memo said.

Nationals from the 19 countries affected by the immigration halt were already under some form of entry ban. In June, Trump issued a presidential proclamation fully barring nationals from 12 countries from entering the United States and partially restricting entry to those from the other seven nations.

The Trump administration has intensified its crackdown on immigration since last week's shooting in Washington, D.C., which left one National Guard member dead and another in critical condition.