President Donald Trump's administration on Wednesday imposed sanctions on a major Iranian foundation and the country's intelligence minister, further stepping up pressure before Joe Biden is sworn in.

The Treasury Department said it was freezing any US interests of the Foundation of the Oppressed, officially a charitable organization for the poor that has sweeping interests across the Iranian economy including in oil and mining.

The Treasury Department described the foundation as a "multibillion-dollar economic empire" and "key patronage network" for Supreme Leader Ayatollah Ali Khamenei that operates without government oversight.

Also hit by sanctions was Iran's minister for intelligence and security, Mahmoud Alavi, on human rights grounds, with the United States saying his agency is responsible for beatings and other abuse of political prisoners.

The latest sanctions will have limited practical effect as the Trump administration has already applied sweeping restrictions on Iran, including trying to stop all of its oil exports and blocking its financial system.

But the move comes as Iran offers to return to compliance with a nuclear deal negotiated under former president Barack Obama if Biden lifts sanctions after taking office on January 20.

Outgoing Secretary of State Mike Pompeo, in an indirect response, vowed to keep imposing "painful consequences."

"The Iranian regime seeks a repeat of the failed experiment that lifted sanctions and shipped them huge amounts of cash in exchange for modest nuclear limitations," he said in a statement.

"This is indeed troubling, but even more disturbing is the notion that the United States should fall victim to this nuclear extortion and abandon our sanctions."