The U.S. believes that Russian President Vladimir Putin is preparing for a long conflict in Ukraine, U.S. Director of National Intelligence Avril Haines said on Tuesday.

"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 also said that a Russian victory in the Donbas might not end the war.

The Russian side hasn't responded to the claim.

(With input from Reuters)