Speaking last week in NATO-member Poland, Obama unveiled plans to spend up to $1 billion on supporting and training the armed forces of alliance states bordering Russia.

The White House also said it would review permanent troop deployments in Europe in the light of the Ukraine crisis, but fell short of a firm commitment to put troops on the ground, as sought by Poland as a security guarantee.

“It would be hard to see additional deployment of substantial NATO military forces in central-eastern Europe, even if on a rotational basis, as anything else but a direct violation of provisions of the 1997 Founding Act on relations between Russia and NATO,” Titov said.

“We will be forced to undertake all necessary political and military measures to reliably safeguard our security.”