Some of the billions of dollars of weapons the United States sent to Ukraine has fallen into Iranian hands, a report Friday details.

As Republican lawmakers have stepped up their oversight on U.S. aid to Ukraine, four anonymous sources revealed to CNN some of the weapons provided to Ukraine have been captured by Russian forces and sent to Iran for reverse-engineering.

Those weapons include the Javelin anti-tank and Stinger anti-aircraft missiles that Ukraine has begged the U.S. to send more of. The weapons were likely picked up on the battlefield, the sources told CNN.

According to the report:

In many of those cases, Russia has then flown the equipment to Iran to dismantle and analyze, likely so the Iranian military can attempt to make their own version of the weapons, sources said. Russia believes that continuing to provide captured Western weapons to Iran will incentivize Tehran to maintain its support for Russia’s war in Ukraine, the sources said.

Earlier this month, Republican lawmakers had pressed Department of Defense officials on whether any U.S. weapons have fallen into the wrong hands.

The Pentagon’s top policy official, Colin Kahl, repeatedly insisted that the DOD was not seeing “any evidence of significant diversion” of weapons sent to Ukraine, as previously reported by Breitbart News.

However, he admitted, “I think our assessment is if some of these systems have been diverted, it’s by Russians who have captured things on the battlefield which always happens. But there’s no evidence that the Ukrainians are diverting it to the black market or some other things.”

He also argued that the Ukrainians were asking for more weapons because “they are using everything that we have provided them.”

Officials claimed to CNN that the Ukrainian military “has made it a habit since the beginning of the war to report to the Pentagon any losses of US-provided equipment to Russian forces.”

The U.S. has committed more than $113 billion in aid to Ukraine in less than a year, with more than $32 billion of it in weapons, much of it taken from the U.S. military’s own stocks.

Grilled at the same hearing with Kahl, the Department of Defense Inspector General Robert Storch would not answer whether the U.S. has complied with a 1976 law to make sure it is tracking weapons sent to Ukraine.

He acknowledged some complaints had been made to a hotline set up for missing U.S. weapons in Ukraine, but said those complaints were still under investigation.

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