Iran's parliament passed a bill on Tuesday designating all US forces "terrorists" after the killing of Iranian commander Qassem Suleimani in a US strike last week.
Suleimani, who was the head of Iran's Islamic Revolutionary Guards Quds Force, was killed in a drone strike outside Baghdad International Airport on Friday, ratcheting up tension between Washington and Tehran.
Under the Iranian bill, all US forces and employees of the Pentagon and affiliated organisations, agents and commanders and those who ordered the killing of Suleimani are designated as "terrorists".
"Any aid to these forces, including military, intelligence, financial, technical, service or logistical, will be considered as co-operation in a terrorist act," Iran's parliament said.
Politicians also voted to allocate €200 million (Dh821.5m) to the Quds Force, the foreign operations arm of the IRGC.
The bill was an amended version of a law adopted in April last year that declared the US a "state sponsor of terrorism" and its forces in the region "terror groups". It came after the US designated the IRGC "terrorist organisation".
President Hassan Rouhani on Monday warned Trump to "never threaten" Iran, after the US leader issued a US strike list of 52 targets in the Islamic republic.
Iran's foreign minister, Javad Zarif, also said he has been informed by UN chief Antonio Guterres that Washington has denied him a visa for a planned trip to UN headquarters in New York.
"What we know is that the US State Secretary, in a call to the Secretary General of the United Nations, said: 'We did not have time to issue a visa for Mohammad Javad Zarif and we will not issue a visa'," Mr Zarif said.
Mr Zarif branded the killing last Friday as "state terrorism.”
"This is an act of aggression against Iran, and it amounts to an armed attack against Iran, and we will respond. But we will respond proportionately," he said.
US Secretary of State Mike Pompeo on Tuesday spoke to reporters and accused Mr Zarif of being a propagandist but said that the US always complies with UN headquarters agreements regarding visas for visiting dignitaries. However, he added that he would not comment on specific travel issues.
