The Trump administration is placing an indefinite pause on immigrant visa processing from 75 countries, further restricting the legal routes for entering the US.

The State Department on Wednesday said the administration wants to bring "an end to the abuse" of the system "by those who would extract wealth from the American people" by using welfare and public benefits.

President Donald Trump has sought to limit both illegal and legal crossing into the US since returning to office, and his administration has already halted immigrant visa processing for people from Brazil, Iran, Russia and Somalia.

The order takes effect on 21 January, but a full list of the 75 countries has not yet been released.

"The State Department will use its long-standing authority to deem ineligible potential immigrants who would become a public charge on the United States and exploit the generosity of the American people," said Tommy Pigott, Principal Deputy spokesperson for the US State Department.

The department, led by Secretary of State Marco Rubio, will pause the visa processing while it reassesses its procedures "to prevent the entry of foreign nationals who would take welfare and public benefits", Piggott added.

According to the Associated Press, the State Department has instructed consular officers to halt immigrant visa applications from the affected countries. But the suspension will not apply to non-immigrant, temporary tourist, or business visas.

In recent months, the State Department has increased restrictions on migration from countries Trump has deemed a threat to national security, including Russia, Iran and Afghanistan and several countries in Africa.

After an immigrant from Afghanistan was charged in the November in the shooting of two National Guard members in Washington, DC, the administration banned or limited the entry of nationals of 19 countries. In December, it expanded the travel ban to people from five additional countries and those travelling on Palestinian Authority-issued documents.

Asylum cases, citizenship processing and green card applications for immigrants from the initial 19 countries in the ban have also been paused.