Washington (CNN) -- The United States will name Iran, as well as its Central Bank, as a "primary money laundering concern" Monday, but will not place sanctions directly on the bank, a senior Treasury Department official said.
The United States will also sanction a number of Iranian companies allegedly supporting Iran's nuclear program, the official said.
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."
U.S. 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.
U.S. sanctions already prohibit American companies from doing business with Iran.
The United Kingdom also announced Monday it will impose fresh sanctions against Iran, cutting all financial ties with the country over concerns about its nuclear program.
U.S. diplomatic sources told CNN Saturday that the goal of the new measures is to bar foreign companies from doing business with Iran's petrochemical industry by threatening to ban them from U.S. markets. The sources did not want to be named because they are not authorized to speak on record before officials roll out the sanctions.
Plans for the additional sanctions come on the heels of a report by the U.N. nuclear watchdog agency detailing evidence that the Iranian regime is developing the technology needed to build a nuclear weapon.
Israeli Defense Minister Ehud Barak told CNN's Fareed Zakaria on Sunday that Iran is probably less than a year away from reaching the point at which it will be too late to stop its nuclear program.
"It's true that it wouldn't take three years, probably three quarters, before no one can do anything practically about it because the Iranians are gradually, deliberately entering into what I call a zone of immunity, by widening the redundancy of their plan, making it spread over many more sites," Barak said on "Fareed Zakaria GPS."
On Friday, the International Atomic Energy Agency board of governors issued a resolution expressing "deep and increasing concern about the unresolved issues regarding the Iranian nuclear program." But the U.N. agency's resolution did not threaten action to curb Iran's nuclear ambitions.
Iran insists its nuclear program is peaceful and has called the U.N. watchdog's report "unbalanced" and "politically motivated."
The Obama administration is facing increased pressure from Congress to turn up the heat on Iran, including sanctioning the Central Bank.
Last week, Republican Sen. Mark Kirk introduced an amendment that would impose sanctions on foreign financial institutions that do business with the Central Bank.
U.S. officials have said the administration has been reluctant to cut off the bank out of concern it could drive up oil prices and hurt the U.S. economy.
But the diplomatic sources said the United States has discussed possible sanctions on the bank that would limit some financial transactions, but not cut it off completely.
CNN's Elise Labott contributed to this report.