At the same time, Washington no longer intends to work on the restoration of the agreement on Iran's nuclear program.
Read also: Iran ready to send more drones, missiles to Russia for its war against Ukraine, reports Reuters
"Iran is not interested in a deal and we're focused on other things," said Malley.
"Right now we can make a difference in trying to deter and disrupt the provision of weapons to Russia and trying to support the fundamental aspirations of the Iranian people."
Read also: US does not confirm Russia has Iranian missiles
He stressed that the U.S. goal is to "disrupt, delay, deter and sanction" the supply of weapons to Russia from Iran. The envoy noted that possible supplies of missiles to Russia or assistance in the organization of weapons production "would be crossing new lines".
Russia has received hundreds of combat drones from Iran, and is using three types of them against Ukraine: the Mohajer-6, the Shahed-129, and the Shahed-191. According to President Volodymyr Zelenskyy, Moscow has ordered a total of 2,400 drones of the latter type from Tehran.
Read also: US confirms Iranian drone transfer to Russia
Earlier, Iranian Foreign Minister Hossein Amir-Abdollahian admitted for the first time that Tehran had indeed handed over drones to Russia, but claimed that it happened before the start of the full-scale war against Ukraine.
Washington refuted this and stressed that Iran handed over drones to Russia in the summer of 2022, and also sent its military specialists to occupied Ukrainian territories to train the Russian armed forces.
Read also: Switzerland joins EU in sanctioning Iran over supply of drones to Russia
Earlier reports have indicated a number of Iranian military trainers have perished in strikes on Russian facilities in occupied Crimea.