The West should not rule out sending weapons and other military equipment to help the Ukrainian army in its war against pro-Russian separatists, NATO's top military commander said on Saturday.

The comments by U.S. Air Force Gen. Philip Breedlove were his strongest public intervention yet in the debate going on in Washington over whether the United States should send defensive weapons to help the Ukrainian government forces.

"I don't think we should preclude out of hand the possibility of the military option," Breedlove, NATO's Supreme Allied Commander, Europe, told a group of reporters at the annual Munich Security Conference.

He said he was referring to providing weapons or capabilities, not sending soldiers. "There is no conversation about boots on the ground," he said.

"The Ukrainians have been straightforward in their request to all the nations of NATO and other nations as well about the capabilities they need to address artillery problems, to address communications problems and jamming problems," he said. "The Ukrainians have asked for help in all of those areas and those are the areas that nations are discussing."

Breedlove also said proposals put forward by Russian President Vladimir Putin to end the conflict in eastern Ukraine were "completely unacceptable."