“I cannot confirm the reports that the transfer has happened,” Kirby said in Washington on Monday.
Such a scenario would have a deleterious effects on both Ukraine and the Middle East, he added.
CNN and the Wall Street Journal reported last week, citing unidentified sources, that Iran had transferred short-range ballistic missiles to Russia, as Moscow continues to wage war in Ukraine more than two and a half years after its 2022 invasion.
A senior Iranian official denied the reports earlier on Monday, describing them as “psychological warfare”.
Deputy Commander of Iran’s Khatam Al-Anbiya Central Headquarters Fazlollah Nozari was quoted by the Iranian Labour News Agency as saying: “No missile was sent to Russia and this claim is a kind of psychological warfare.”
“Iran does not support any of the parties to the Ukraine-Russia conflict,” Nozari added.
Kremlin spokesman Dmitry Peskov has also said he had seen the report but that not all such reports were correct.
“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 ones,” Peskov told reporters on Monday.
Ukraine announced last week that deepening military cooperation between Tehran and Moscow was a threat to Ukraine, Europe and the Middle East, and called on the international community to increase pressure on Iran and Russia.
The United States also said on Friday any Iranian transfer of ballistic missiles to Russia would mark a sharp escalation in the Ukraine war.
That language was echoed on Monday by a NATO spokesperson, who stated the Western military alliance was aware of the media reports but would not be drawn on whether they were accurate.
“As Allies have stated previously, any transfer of ballistic missiles and related technology by Iran to Russia would represent a substantial escalation,” the spokesperson added.
Moscow has accused Kyiv’s allies of escalating the war by providing weapons used in Ukraine’s recent incursion into Russia’s Kursk region, and has threatened to respond.
