US National Security Adviser Jake Sullivan Wednesday warned of the threat of Russian President Vladimir Putin's attempts to deepen relations with Iran to could harm Ukrainian civilians. 

Sullivan made the remarks from Air Force One as President Joe Biden embarked on his tour to the Middle East. 

"Russia deepening an alliance with Iran to kill Ukrainians is something that the whole world should look at and see as a profound threat," Sullivan said.

His comments come as US officials have said Iran is preparing to help supply Russia with several hundred drones, including some that are weapons-capable, to use in Ukraine, while Putin is expected to visit Tehran next week. Sullivan called the timing of the Putin trip "interesting."

An official of Ukrainian President Volodymyr Zelenskyy’s political party told Iran International on July 12 that the news of Tehran planning to arm Russia with drones has shocked Ukrainian officials.

Yevheniia Kravchuk, who is also a member of the Ukrainian parliament, said that Tehran’s decision would lead to the death of more Ukrainian civilians.

Sullivan said on July 11 that “Our information indicates that the Iranian government is preparing to provide Russia with up to several hundred UAVs, including weapons-capable UAVs on an expedited timeline,” adding that Iran is “preparing to train Russian forces to use these UAVs with initial training sessions slated to begin as soon as early July.”

Tehran has not officially taken side with Russia on Ukraine but many officials, including President Ebrahim Raisi, have implicitly accused Ukraine of instigating Russia to attack by seeking to join NATO.