The effort is part of a broader U.S. campaign, announced last week by the State Department, meant to make sure that weapons provided to Ukraine don’t end up in the hands of Russian troops, their proxies or other extremist groups.UN nuclear agency starts probe of Russian dirty bomb claimUkrainians grapple with power outages as winter approachesHeavy Russian barrage on Ukraine, no water for much of KyivRussia recruiting U.S.-trained Afghan commandos, vets sayU.S. officials have faced persistent questions from some members of Congress over how the administration is accounting for the billions of dollars in arms that have been sent to Ukraine over the past year.But the administration had been reluctant to detail its work on that front due to concerns about the state of the conflict and fears it might tip off would-be smugglers to potential evasion techniques.The State Department said that so far Ukraine’s intense demand for weapons on the battlefield appears to be impeding black-market proliferation of small arms, portable air defense systems and anti-tank weapons such as Javelins.It said the main problem has been the seizure of weapons by Russian forces as they take ground, and warned that Moscow can use them to develop countermeasures or conduct false-flag operations."