Britain, Germany and the United States advanced plans on Tuesday to spearhead a new NATO force on Russia's border next year, and Russian President Vladimir Putin ordered snap checks on combat readiness across the armed forces.

Weeks before a critical NATO summit in Warsaw, three of NATO's biggest military powers said they would each command a battalion across the eastern flank to help deter any show of force such as that deployed by Moscow in Crimea in 2014.

"That should send a very strong signal of our determination to defend the Baltic states and Poland in the face of continued Russian aggression," British Defense Secretary Michael Fallon said.