U.S. President Donald Trump's administration is considering significantly expanding its travel restrictions by potentially banning citizens of 36 additional countries from entering the United States, according to an internal State Department cable seen by Reuters.

Earlier this month, the Republican president signed a proclamation that banned the entry of citizens from 12 countries, saying the move was needed to protect the United States against "foreign terrorists" and other national security threats.

The directive was part of an immigration crackdown Trump launched this year at the start of his second term, which has included the deportation to El Salvador of hundreds of Venezuelans suspected of being gang members, as well as efforts to deny enrollments of some foreign students from U.S. universities and deport others, according to Reuters.

In an internal diplomatic cable signed by U.S. Secretary of State Marco Rubio, the State Department outlined a dozen concerns about the countries in question and sought corrective action.