By Idrees Ali and Phil Stewart
WASHINGTON (Reuters) -The United States has long asked Ukraine not to use U.S.-provided military equipment to carry out attacks inside Russian territory, the top U.S. general said on Thursday, following accusations by Russia that pro-Ukrainian militia used U.S. armored vehicles.
Army General Mark Milley, chairman of the Joint Chiefs of Staff, said his office was looking into social media imagery of vehicles and military hardware in a cross-border incursion on Monday by militia in the Russian region of Belgorod.
"I can't say with definitive accuracy right this minute to you whether that - and I saw the same video - whether that's U.S. supplied equipment or not, what was the nature of the attack, who did what to whom," Milley told a press conference at the Pentagon.
"I can't say that with definitiveness right this minute, but I can say that we have asked the Ukrainians not to use U.S.-supplied equipment for direct attacks into Russia."
Footage of some destroyed vehicles released by the Russian defense ministry showed U.S.-made military hardware such as Humvee military trucks. Reuters was able to confirm the location of damaged vehicles and surrounding details shown in the video, though could not verify the date it was filmed.
Ukraine's government denied any role in the Belgorod raid, which has been claimed by two anti-Kremlin armed groups made up of Russian nationals, some of whom are far-right figures.
Ukraine has said in the past that it will not use longer-range weapons pledged by the United States to hit Russian territory and will only target Russian units on occupied Ukrainian territory.
Milley said restrictions on U.S. support to Ukraine following Russia's February 2022 invasion was aimed at ensuring Kyiv's self-defense against Russian forces inside Ukraine.
"Why is that? Because we don't want - this is a Ukrainian war. It is not a war between the United States and Russia. It's not a war between NATO and Russia," Milley said.
The questions over Ukrainian use of U.S.-provided weaponry arose after President Joe Biden backed training Ukrainian pilots to fly U.S.-made F-16 fighter jets, which Russia had previously warned the West against doing.
"It is no secret for us that more and more equipment is being delivered to Ukraine's armed forces," Kremlin spokesman Dmitry Peskov told reporters on Wednesday when asked about the militias use of U.S.-made hardware.
Biden said he had received a "flat assurance" from Ukrainian President Volodymyr Zelenskiy that he would not use Western-provided F-16 fighter jets to go into Russian territory.
(Reporting by Idrees Ali, Phil Stewart and Doina Chiacu; editing by Diane Craft and Grant McCool)