The United States and Britain have both warned of new Iranian arms shipments to Russia.
Washington immediately announced new sanctions against Moscow.
In addition to ballistic missiles, Russia is also to receive drones from Iran – the energy infrastructure in Ukraine was recently attacked and severely damaged with drones of this type.
Because of this damage, the Ukrainians must already be prepared for a harsh winter with many power cuts.
US warns against Iranian military aid to Moscow
The United States is concerned about what it sees as growing military cooperation between Russia and Iran.
Among other things, Moscow is offering Tehran support "at an unprecedented level", thereby transforming the relationship between the two states into a "full defense partnership," said US National Security Council spokesman John Kirby.
For its part, Moscow again denied Iranian arms deliveries.
Moscow-Tehran cooperation is "harmful" to Ukraine, Iran's neighbors and the entire world, Kirby said.
Western states have accused Iran of supplying Russia with combat drones for its war of aggression against Ukraine.
Iran confirmed in November that it had delivered drones to Russia.
However, these were delivered before the Russian invasion of Ukraine, according to Tehran.
At a Security Council meeting on the Ukraine war, Russia's UN ambassador again denied reports of arms deliveries from Tehran to his country.
"Russia's military-industrial complex is very strong and does not need anyone's support," said Vasily Nebensia, noting that Moscow had "several times" denied the allegations.
On the other hand, US Security Council spokesman Kirby reported, among other things, intelligence information according to which Moscow and Tehran are considering a “joint production line for combat drones in Russia”.
"We urge Iran to change course," Kirby said.
He also announced US sanctions against three Russia-based companies involved in “the acquisition and use of Iranian drones.”
London: Russia wants to buy more arms from Iran
“Russia is now trying to acquire more weapons, including hundreds of ballistic missiles.
In return, Russia is offering Iran an unprecedented level of military and technical assistance,” said British Ambassador to the UN, Barbara Woodward, in New York.
British Foreign Secretary James Cleverly said in London that Iran is now one of Russia's biggest military supporters.
"Through these dirty deals, the Iranian regime sent hundreds of drones to Russia, which were used to attack Ukraine's critical infrastructure and kill civilians." Moscow, in turn, is offering military and technical support to the regime in Tehran.
Zelenskyy: Russia has brought "hell" to Ukraine
With its invasion of Ukraine, the Russian army brought "hell under the Russian flag" into the country, according to the head of state Volodymyr Zelenskyy.
The situation is “very difficult,” Zelensky said in his daily video address, especially in the frontline areas of the Donbass in eastern Ukraine.
He listed the focal points of Bakhmut, Soledar and Kremnina.
"There hasn't been any living space in these areas for a long time that hasn't been damaged by shells."