East-West tensions remain high after NATO vowed to cut cooperation with Moscow over its intervention in Crimea and what it called an intimidating build up of Russian troops along Ukraine’s border.

Ukrainian forces have been carrying out military exercises. Its interim government has pledged financial support for the army despite the country’s current economic difficulties.

NATO General Secretary Anders Fogh Rasmussen added a further warning to Russia on day two of the military alliance’s meeting in Brussels:

“If Russia were to intervene further in Ukraine, I wouldn’t hesitate to call it an historic mistake. That would lead to further isolation, international isolation of Russia. It would have far reaching consequences.”

In a move to reassure nervous eastern European states the US has already beefed up planned military exercises with Bulgaria. It is also bolstering the size of its Europe-based crisis response force by sending extra Marines to a Romanian base near the Black Sea.