Iran's parliament passed a bill on Tuesday requiring the government take firm steps to respond to "terrorist actions" by U.S. forces, state TV reported, retaliating against Washington's blacklisting of the country's elite Revolutionary Guards.
President Donald Trump on April 8 designated the Islamic Revolutionary Guards Corps (IRGC) a foreign terrorist group, in an unprecedented step that drew Iranian condemnation and raised concerns about retaliatory attacks on U.S. forces.
Tehran reacted to the designation, which took effect on April 15, by naming the U.S. Central Command (CENTCOM) a terrorist organization and the U.S. government a sponsor of terrorism.
"The bill authorizes the government to take firm and retaliatory measures against terrorist activities of American forces that endangers Iran's interests," TV reported.
"The government should use legal, political and diplomatic measures in response to the American actions."
Highly loyal to Iran's Supreme Leader Ayatollah Ali Khamenei, the IRGC is a powerful force which controls much of the Iranian economy and wields political influence in the country's faction-ridden clerical establishment.
The semi-official Tasnim news agency said some 168 lawmakers out of 210 present at the parliament voted for the bill.
Tensions have been on the rise between Tehran and Washington since last year, when Trump withdrew from a 2015 nuclear deal between Iran and six major powers and reimposed sanctions on the country.
In recent years, there have been periodic confrontations between the IRGC and U.S. military in the Gulf.
The new chief commander of the IRGC Hossein Salami, appointed after the U.S. blacklisting, has warned in the past that Iran could use its cruise and ballistic missiles and drones, mines, speedboats, and missile launchers in the Gulf area to confront the United States.
The Trump administration, which has taken a hard line on Iran, said in a statement on Monday that the president has decided not to reissue waivers in May allowing importers to buy Iranian oil without facing U.S. sanctions.
A commander of Iran's IRGC said on Monday that Tehran would block all exports through the Strait of Hormuz in the Gulf if Tehran is barred from using the waterway, where a fifth of global oil consumption passes on its way from Middle East producers to major markets.