Antony Blinken, during a visit to the UK, said Moscow had received the missiles and that Russian military personnel had been trained on how to use them in Iran.
Iran has sent short-range ballistic missiles to Russia and the Kremlin “will likely use them within weeks in Ukraine”, the US secretary of state has said.
Speaking during a visit to the UK, Antony Blinken said the development was “a threat to all of Europe” and showed how Iran’s “destabilising influence reaches far beyond the Middle East”.
He told a news conference: “Dozens of Russian military personnel have been trained in Iran to use the Fath-360 close range ballistic missile system, which has a maximum range of 75 miles.
“Russia has now received shipments of these ballistic missiles and will likely use them within weeks in Ukraine against Ukrainians.
“Russia has an array of its own ballistic missiles, but the supply of Iranian missiles enables Russia to use more of its arsenal for targets that are further from the front line.”
However, when asked if he would approve Ukraine’s use of the Storm Shadow long-range missiles to strike targets inside Russia, Mr Lammy said he would not comment on “operational issues”.
The US will be announcing further sanctions on Iran later on Tuesday, Mr Blinken said, including further measures against Iran Air.
He said other countries were also expected to announce fresh sanctions.
However, the Ukrainian president’s chief of staff said imposing sanctions on Iran for supplying Moscow with ballistic missiles was not enough, and allies should allow Kyiv to carry out strikes deep into Russia using Western weapons.
“We also need permission to use Western weapons against military targets on the territory of the Russian Federation, deliveries of longer-range missiles, and strengthening our air defences,” the official, Andriy Yermak, said on Telegram.
Mr Lammy and Mr Blinken revealed they would be travelling together to Kyiv later this week, in what Mr Lammy described as the “first joint visit of this kind for well over a decade”.
Mr Blinken said Russia and Iran’s relationship was a “two-way street”, with the Kremlin sharing technology with Iran, including on nuclear issues and space information.
“So, as Iran’s destabilising activity spread, so does Russia, sowing even greater insecurity in their regions and around the world,” he said.
He added the US has been sharing intelligence behind the discovery with allies and partners “and working together to ensure that there will be significant economic consequences for Tehran’s actions”.
Nasser Kanani, spokesperson for Iran’s Ministry of Foreign Affairs, condemned the UK, France, and Germany for cancelling bilateral air service agreements and the sanctioning of Iran Air.