WASHINGTON — The Pentagon ordered 8,500 troops on higher alert Monday to potentially deploy to Europe as part of a NATO “response force” amid growing concern that Russia could soon make a military move on Ukraine. President Joe Biden consulted with key European leaders, underscoring U.S. solidarity with allies there.

Putting the U.S.-based troops on alert for Europe suggested diminishing hope that Russian President Vladimir Putin will back away from what Biden himself has said looks like a threat to invade Ukraine.

Pentagon press secretary John Kirby said about 8,500 U.S.-based troops are being put on alert for possible deployment — not to Ukraine but to NATO territory in Eastern Europe as part of an alliance force meant to signal a unified commitment to deter any wider Putin aggression.