Iran could supply Russia with ballistic missiles and drones to use in its war in Ukraine, Nato Secretary-General Jens Stoltenberg has said.
Ukraine and its western allies, including the US, said Tehran had already sent drones to Russia.
On Tuesday, it was reported that Iran was preparing a shipment of 1,000 missiles and drones destined for Russia.
“We see Iran offering drones and considering ballistic missile deliveries to Russia,” Mr Stoltenberg said at a news conference in Istanbul on Thursday.
“This is unacceptable. No country should provide support to Moscow in this illegal war.”
Ukraine has said about 400 Iranian drones have already been used against the civilian population of Ukraine, with Russia ordering about 2,000. Iran has rejected the allegation.
Mr Stoltenberg said Russian President Vladimir Putin's plans were failing in Ukraine, resulting in him “responding with more brutality”.
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“In recent weeks, we have seen dozens of drone and missile strikes across Ukraine, including on critical infrastructure,” Mr Stoltenberg said.
He accused Russia of “cruelly and deliberately depriving Ukrainian civilians of heating, water and electricity at the outset of winter”.
On Tuesday, experts told The National that Russia's campaign would receive a major lift with the delivery of hundreds more “kamikaze” drones and short-range ballistic missiles.
The consignment is being closely monitored by western intelligence services, particularly as it will be the first occasion that Iran has exported surface-to-surface missiles, potentially the Shahab or Zolfaghar weapons.
The arms are expected to arrive in Russian territory before the end of this year.
