WASHINGTON (AP) — 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 heightened 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 neighboring Ukraine.

At stake, beyond the future of Ukraine, is the cred...