News reports say the United States provided intelligence that helped Ukraine sink the Russian guided-missile cruiser Moskva last month.
The reports, by The New York Times and NBC News, follow other U.S. reports that said Washington provided Ukrainian forces with intelligence to target Russian generals on the battlefield.
An unusual number of Russian generals have been killed during more than two months of fighting in Ukraine, with at least eight confirmed.
The reports added to concerns that Washington is helping to escalate the war and could provoke a stronger response from Moscow by, for example, targeting the convoys supplying Ukrainian forces with NATO weaponry
NBC News reported on May 5 that the United States had helped locate the Moskva in the Black Sea, at the request of the Ukrainian military. But, according to The Washington Post and the Times, the U.S. government had no knowledge of Ukraine's plans.
The Moskva, which was the flagship of Russia's Black Sea Fleet, sank in mid-April after being hit with what is widely believed to be Ukrainian anti-ship missiles.
Moscow has denied that, saying only that a fire broke out on board the ship.
On May 4, the Times reported that U.S. officials had provided Ukraine details on the Russian military's mobile headquarters. Ukrainian forces used that information to help target Russian officers.
Pentagon spokesman John Kirby said on May 5 it was true that the United States supplied Kyiv's forces with military intelligence.
But he added that"We do not provide intelligence on the location of senior military leaders on the battlefield or participate in the targeting decisions of the Ukrainian military."
On May 6, White House press secretary Jen Psaki said media reports that U.S. intelligence aided Ukraine to take out Russian generals are not accurate, without being more specific.