The United States formally accused Iran on Tuesday of supplying short-range ballistic missiles to Russia for its war in Ukraine and will take measures to punish those involved.
US Secretary of State Antony Blinken, speaking alongside British Foreign Secretary David Lammy during a visit to London, said that sanctions would be announced later Tuesday.
"Russia has now received shipments of these ballistic missiles and will likely use them within weeks in Ukraine, against Ukrainians," Blinken said.
His comments came as he and Lammy prepare to make a joint visit to Ukraine on Wednesday.
Word of the alleged transfers began to emerge over the weekend with reports that intelligence indicated they were underway, according to US officials who spoke on condition of anonymity.
Blinken said Tuesday that the transfers appear to have been completed.
The European Union said Monday its allies had shared "credible" intelligence that Iran had supplied Russia with ballistic missiles, after Washington warned would be met with "significant consequences".
Stano added that "the EU leaders' unanimous position has always been clear. The European Union will respond swiftly and in coordination with international partners, including with new and significant restrictive measures against Iran".
Iranian foreign ministry spokesman Nasser Kanani said during a weekly press conference: "We strongly reject the claims on Iran's role in exporting arms to one side of the war."
The West has been warning Tehran against sending Russia missiles for months, and the EU has already repeatedly hit Iran with sanctions for supplying drones to Moscow for the war in Ukraine.
"Any transfer of Iranian ballistic missiles to Russia would represent a dramatic escalation in Iran's support for Russia's war of aggression against Ukraine," State Department spokesman Vedant Patel told journalists.
"We have been clear... that we're prepared to deliver significant consequences."
'Severe' response
The Kremlin did not issue a denial on Monday when asked specifically about the initial Wall Street Journal report that Iran had sent missiles.
"We have seen this report, it is not every time that this kind of information is true," Kremlin spokesman Dmitry Peskov said.
"Iran is our important partner, we are developing our trade and economic relations, we are developing our cooperation and dialogue in all possible areas, including the most sensitive areas."
The United States had previously said any deliveries would invoke a "severe" response and damage Tehran's efforts to improve relations with the West following the election of reformist Masoud Pezeshkian as president.
Faced with punishing Western sanctions, Moscow has turned to Iran and North Korea for weapons supplies to keep its war machine going in Ukraine.
Ukraine says it has been attacked with Iranian-designed Shahed drones on an almost daily basis from Russia and has found fragments of North Korean missiles on its territory.
The Kremlin has once again stepped up its bombing campaign against Ukraine's key infrastructure ahead of winter.