The US Defense Department said on Tuesday that Ukraine has received additional aircraft and parts as it battles a Russian invasion.

Defense Department Press Secretary John Kirby did not say which countries provided the aircraft, but said the United States helped transport spare parts.

Kirby said Ukraine now has "more operable fighter aircraft than they had two weeks ago." He said, "That's because other nations who have experience with those kinds of aircraft have been able to help them get more aircraft up and running."

Ukraine is requesting further military assistance from the US and other Western nations, as Russian forces intensify their assault on eastern Ukraine.