WASHINGTON: There is "no evidence" Ukraine is misusing the tens of billions in aid provided since Russia invaded last year, a senior Pentagon official told lawmakers on Tuesday.

Members of the House Armed Services Committee questioned Defense Department number three Colin Kahl and two other officials for two and a half hours, as Republicans seek to step up oversight of American aid to Ukraine after taking control of the lower chamber of Congress.

"There's no evidence that the Ukrainians are diverting it to the black market," Kahl told lawmakers of assistance to Kyiv.

"That's not surprising given the intensity of the fight and the fact that they are clearly using what we are providing them and what our allies and partners are providing them to maximum effect," he said.

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"I think our assessment is if some of these systems have been diverted, it's by Russians who have captured things on the battlefield."

The Defense Department's inspector general, Robert Storch, told the committee that there are a "significant number" of people in the region overseeing the Ukraine supply and training mission, and that information is also being obtained from US military personnel at the embassy in Kyiv.

"We have not substantiated any such instances" of sensitive weapons such as Stinger missiles being illicitly diverted, Storch said.

The United States has spearheaded the push for international support for Ukraine, quickly forging an international coalition to back Kyiv after Russia invaded in February 2022 and coordinating aid from dozens of countries.