Washington (CNN) -- The Obama administration plans to impose fresh sanctions against Iran's petrochemical industry, diplomatic sources familiar with the plans said Friday.
U.S. sanctions already prohibit American companies from doing business with Iran.
The goal of the new measures is to bar foreign companies from doing business with Iran's petrochemical industry by threatening them with being banned from U.S. markets, the sources said.
European nations are expected to announce similar measures when the European Union leaders meet next week, the sources said. The sources did not want to be named because they are not authorized to speak on record before officials roll out the sanctions.
The measures, which the sources said are expected to be announced early Monday, build on existing sanctions on Iran's oil and gas industry.
Plans for the additional sanctions come on the heels of a report by the U.N. nuclear watchdog IAEA detailing evidence that the Iranian regime was developing the technology needed to build a nuclear weapon.
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 Iranian central bank.
This week, Republican Sen. Mark Kirk introduced an amendment that would impose sanctions on foreign financial institutions that do business with Iran's central bank.
U.S. officials have said the administration has been reluctant to cut off the central bank out of concern it could drive up oil prices and hurt the U.S. economy.
But the diplomatic sources said the U.S. has discussed some possible sanctions on the bank by limiting some financial transactions, but not cutting it off completely.