NATO's top military commander has warned over the build-up of Russian troops on the Ukrainian border. NATO's Supreme Allied Commander Europe, Philip Breedlove, describes Russian forces there as "very very sizeable and very very ready".

He says the 28-nation alliance is particularly concerned about the Trans-Dniester region, a narrow strip of land between the Dniester River and Ukrainian southwestern border.

Breedlove also accuses Russia of acting more like an adversary than a partner. He's urging NATO to rethink the positioning and readiness of its forces in eastern Europe.

Russia maintains that the number of its forces east of Ukraine is in line with international agreements.