Russia's war in Ukraine is at a "bit of a stalemate" and Russian President Vladimir Putin appears to be preparing for a long conflict, top U.S. intelligence officials said.
Russia, which calls the invasion "a special military operation," poured more troops into Ukraine for a huge offensive
last month in the eastern part of the country but its gains have been slow.
Russia's assault on Kyiv was beaten back in March by Ukrainian resistance.
"The Russians aren't winning and the Ukrainians aren't winning and we're at a bit of a stalemate here," Lieutenant General Scott Berrier, the head of the Defense Intelligence Agency, said before the Senate Armed Services Committee.
He added that so far, between eight and 10 Russian generals have been killed.
Pentagon spokesman John Kirby said that while Russia had made no major gains in Donbas, its troops were making incremental progress.
The war has claimed thousands of civilian lives, sent millions of Ukrainians fleeing and reduced cities to rubble. Moscow has little to show for it beyond a strip of territory in the south and marginal gains in the east.
Putin urged Russians to battle in a defiant Victory Day speech on Monday but was silent about plans for any escalation in Ukraine despite Western warnings that he might use his Red Square address to order a mobilization.
During the same hearing, Director of National Intelligence Avril Haines said a Russian victory in the Donbas region in eastern Ukraine might not end the war.
"We assess President Putin is preparing for a prolonged conflict in Ukraine during which he still intends to achieve goals beyond the Donbas," Haines told lawmakers.
She said the United States had indications that Russia wanted to extend a land-bridge to Moldova's breakaway region of Transdniestria.