Washington has warned Tehran of "rapid and severe" consequences if reports are confirmed that it is planning to send hundreds of ballistic missiles to Russia.
"We are prepared for a swift and tough response if Iran were to send ballistic missiles, which in our opinion would represent a dramatic escalation of Iran's support for Russia's war of aggression against Ukraine," State Department spokesman Vedant Patel told reporters.
The warning coincides with a warning issued earlier this year by the US, after Reuters – citing six unnamed sources – reported that Iran had sent "a large number" of powerful surface-to-ground ballistic missiles to Russia.
The United States and the European Union have imposed sanctions on Tehran's ballistic missile program over concerns that iran could send them to allies and associates in the Middle East and Russia so that Moscow can use them against Ukraine.
Russia is short of weapons as it continues its invasion of Ukraine — which began in 2022 — and is also facing significant losses of troops and equipment, prompting it to seek allies such as Iran and North Korea to fill the stockpile of weapons.
On February 22, the US also warned Iran of a "swift and tough" response from the international community if Tehran were to give Ballistic Missiles to Russia.
U.S. national security spokesman John Kirby said washington had not yet confirmed whether the missiles had been transferred from Iran and Russia, but added that the report appeared to be accurate.
Tehran has offered Russia drones, bombs and ammunition for artillery, according to U.S. and Ukrainian officials after evidence of the use of Iranian-made Shahed drones in attacks on Ukraine, prompting Western states to impose additional sanctions.
"Iranian officials have also continued to deny that they have provided any drones to Russia, despite evidence being evident that Russia repeatedly uses these drones during attacks against civilians in Ukraine, against civilian infrastructure," Patel told reporters.
Iran's new President Masoud Pezeshkian, widely regarded as a reformist, has spoken of the hope of improving relations with the West, but Patel expressed skepticism.
In January, the Us State Department, along with the EU and other countries issued a similar warning to North Korea over its arms sales to Russia.