UK, US united over tackling Iran's influence: top envoys

British Foreign Secretary David Lammy and US Secretary of State Antony Blinken, who will jointly visit Kiev this week, have said they are united on the need to tackle Iran's influence in the Middle East and Ukraine.

"(We are) completely aligned on the need to tackle Iran's malign activity in the region and beyond," Lammy told reporters on Tuesday beside Blinken, who is visiting Britain.

"We're seeing a disturbing pattern of greater Iranian support for the Kremlin's illegal group, and we discussed today our shared commitment to holding Tehran to account for their undermining of global stability."

Lammy said he and Blinken would travel to Kiev this week, the first joint visit of this kind for more than a decade.

'A dramatic escalation'

Russia has received ballistic missiles from Iran and will likely use them in Ukraine within weeks, Blinken said, warning that cooperation between Moscow and Tehran threatens wider European security.

He also said Washington had privately warned Iran that providing ballistic missiles to Russia would "constitute a dramatic escalation" and said new sanctions would be imposed later on Tuesday.

"Russia has now received shipments with these ballistic missiles, and will likely use them within weeks in Ukraine, against Ukraine," Blinken said, citing intelligence that he said has been shared with US allies and partners around the world.

The supply of Iranian missiles enables Russia to use more of its arsenal for targets that are further from the front line in Ukraine, Blinken said.

"This development and the growing cooperation between Russia and Iran threatens European security and demonstrates how Iran's destabilising influence reaches far beyond the Middle East."

Russia was also sharing technology with Iran, including on nuclear issues, he added.

Additional US sanctions on Iran will include the airline Iran Air, and other countries are also expected to announce new sanctions, Blinken said.