At a regular meeting of Ukraine's allies at Ramstein U.S. Air Base in Germany, Volodymyr Zelenskyy repeated his plea for Western nations to supply more long-range missiles and lift restrictions on using them to hit targets such as airfields inside Russia.

Austin said Washington and its allies would continue to give strong support to Ukraine in fighting Russia's invasion, announcing another $250 million in U.S. security assistance.

But, questioned by reporters, the Pentagon chief pushed back on the idea that allowing deep strikes inside Russia with Western weapons would be a game-changer.

He said Russia had already moved aircraft that launch glide bombs into Ukraine beyond the range of U.S.-supplied ATACM missiles.

"There's no one capability that will in and of itself be decisive in this campaign," Austin told reporters at the end of the meeting.

He also said Ukraine had capabilities of its own - such as drones - to hit targets inside Russia that were beyond the reach of ATACM and British-supplied Storm Shadow missiles.

"There are a lot of targets in Russia - big country, obviously," Austin said. "And there's a lot of capability that Ukraine has in terms of UAVs (unmanned aerial vehicles) and other things to address those targets."