Some "55 million foreigners" who hold a valid visa are subject to increased controls, the US State Department announced on Thursday, as the Trump administration intensifies its repressive immigration policy.

"The Department's ongoing screening includes all of the more than 55 million foreign nationals who currently hold valid U.S. visas," a State Department official said on condition of anonymity.

He said the State Department could revoke visas "whenever there is evidence of possible ineligibility" ranging from overstaying, criminal activity or violations of the law, including drunk driving, or threats to public safety, as well as any "form of terrorist activity or support for a terrorist organization."

"As part of our vetting process, we review all available information, including law enforcement or immigration records, as well as any other information revealed after the visa is issued," the official said in an email to reporters.

On Monday, the State Department announced that it had revoked the visas of more than 6,000 foreign students, including about 4,000 for violating the law.

The United States has revoked "more than twice as many visas, including nearly four times as many student visas, as during the same period last year" under the administration of Democratic President Joe Biden, he noted.

Upon returning to the White House in January, President Donald Trump made the fight against illegal immigration a top priority, referring to an "invasion" of the United States by "criminals from abroad" and speaking extensively about immigrant deportations.

His mass expulsion program has certainly been thwarted or slowed by multiple court decisions, which he has repeatedly expressed outrage about.

But his government is also hunting down anything that appears "anti-American" or goes against US foreign policy interests.

The US government said on Tuesday that it would look for "anti-American" opinions, including on social media, when deciding on the right to reside in the United States.

The official stopped short of saying that all 55 million visas granted by the United States were under scrutiny, but he made it clear that they were affected.

The Trump administration has also engaged in a series of battles against universities, revoking thousands of visas and targeting renowned institutions suspected of allowing anti-Semitic ideas to spread on their campuses, particularly in the context of protests against the war in the Gaza Strip.

The benefits of immigration, including the right to live and work in the United States, "remain a privilege, not a right," US Secretary of State Marco Rubio likes to repeat.