The unanimous vote was in response to Major General Qasem Soleimani's assassination, which the U.S. attempted to justify using its own terrorist designation of the Iranian military.
In a move mirroring President Donald Trump's own justification for assassinating Iranian military leader Qasem Soleimani, Iran's Parliament on Tuesday unanimously voted to declare all members of U.S. military leadership "terrorists."
The vote came four days after Trump ordered a drone strike near Baghdad International Airport, killing Soleimani. As the lawmakers voted in favor of the measure, millions of Iranians around the country mourned the general's death as part of a three-day mourning period.
Photos from the parliamentary session showed lawmakers holding up photos of Soleimani as they placed their votes and placing his image on their desks.
Under the Iranian declaration, the Pentagon is officially designated a terrorist organization, and "any aid to these forces, including military, intelligence, financial, technical, service or logistical, will be considered as cooperation in a terrorist act." U.S. military leaders will be subject to Iranian sanctions.
Parliament also voted to allocate $220 million to the Quds Force, the unit of the Islamic Revolutionary Guards Corps (IRGC) which Soleimani led, "to boost their defensive power" and to "avenge" Soleimani's death.
Last April, Trump became the first world leader to designate a sovereign government entity as a terrorist organization when he imposed economic and travel sanctions on the IRGC.
The measure passed Tuesday in Iran was an amendment added to the law Parliament passed in response to Trump's designation, in which lawmakers declared U.S. Central Command a terrorist group and accused the U.S. of state-sponsored terrorism.
Following Trump's decision, critics warned that the president was likely ramping up to escalate tensions with Iran.
"There is an urgent need for Congress to rein Trump in on Iran before he can start a war that will devastate the U.S., Iran, and the Middle East for generations to come," Jamal Abdi, president of the National Iranian American Council (NIAC) said following Trump's decision.
Indeed, the Trump administration used the terrorist designation of the IRGC to justify the assassination of Soleimani, noting when it announced his death that he had headed "a U.S.-designated Foreign Terrorist Organization."
In a statement signed by Iran's 223 members of Parliament Tuesday, the lawmakers wrote that Iran's response to the latest "terrorist act of the criminal U.S. administration" would determine the future of the region.
"If this harsh revenge is proportionate, direct, and military and is taken promptly, America's factious grandeur will be destroyed and U.S.officials will truly understand that the era of hitting and running is over," the lawmakers said in their statement, adding that the main goal of Iranian officials is to achieve the withdrawal of U.S. military presence in the area.
"Furthermore," they wrote, "it is necessary to concentrate on the issue of American military forces' withdrawal from the West Asian region so that this aim will be achieved with the help of the Resistance Axis."