The US will also sanction a number of Iranian companies allegedly supporting Iran's nuclear program, said the official.

The Treasury Department announced that Secretary of State Hillary Clinton and Treasury Secretary Tim Geithner will hold an afternoon news conference "to outline new steps the United States is taking to increase pressure on Iran."

US officials have been considering action against the Central Bank of Iran but became concerned that a full sanction could have a negative effect on the world economy because of the potential impact on oil prices.

A number of congressional members have been calling for sanctions against the bank amid questions about how much the current spate of sanctions are actually working.

US sanctions already prohibit American companies from doing business with Iran.

The United Kingdom also announced on November 21 it will impose fresh sanctions against Iran, cutting all financial ties with the country over concerns about its nuclear program.

CNN