The United States and allies warned Iran on Friday that major Western economies will pile new sanctions on Tehran if it moves forward with an advancing plan to provide ballistic missiles to Russia for its war with Ukraine.

The Biden administration has raised alarms for months that Russia is seeking close-range ballistic missiles from Iran as Moscow struggles to replenish its dwindling supplies.

The US has yet to confirm that missiles have moved from Iran to Russia but US officials are alarmed by comments by Iranian officials that suggest that a deal is imminent.

In September, according to the White House, Iran hosted Russian Defence Minister Sergei Shoigu to show off a range of ballistic missile systems — a moment that sparked US concern that a deal could come together.

US Iran Russia
An Iranian-built missile is displayed during a rally in Tehran in February (Vahid Salemi/AP)

Asked why the deal has not already been consummated, White House national security spokesman John Kirby said he could not “speak for the mullahs”.

The Biden administration has repeatedly sought to make the case that the Kremlin has become reliant on Iran and North Korea for the arms it needs to fight its war against Ukraine and has disclosed intelligence findings that it says show as much.

Russia has acquired and used North Korean ballistic missiles against Ukraine. Ukrainian officials, however, say that North Korean missiles when deployed by Russian forces have frequently missed targets.

Russia has received hundreds of one-way attack drones, as well as drone production-related equipment, from Iran, according to the White House.

The Biden administration also has accused Tehran of providing Russia with materials to build a drone manufacturing plant east of Moscow.

One action that the G7 (Group of Seven) countries are mulling is to prohibit Iran Air, the country’s national air carrier, from flying to Europe, according to a senior Biden administration official.

The official, who was not authorised to comment and insisted on anonymity, declined to preview other sanctions that the US are considering beyond describing the potential action as “significant measures”.

The US and Europe already impose extensive sanctions against Iran targeting individuals as well as limiting the country’s access to trade, financial services, energy, technology and other sectors.

The sanctions on Iran are arguably the most extensive and comprehensive set of sanctions that the US maintains on any country, with thousands of individuals and entities targeted.