BRUSSELS, BELGIUM (CNN) - NATO's military chief warned Wednesday that Russian troops could begin moving on Ukraine within 12 hours of being given an order, amid fears that Moscow could seek to invade its eastern region.
Gen. Philip Breedlove, NATO's supreme allied commander Europe, also told CNN's Christiane Amanpour that with 40,000 troops massed near the border, Russia has all the components necessary to move on Ukraine.
These forces are "supported by fixed-wing aircraft, rotary aircraft, all of the logistics required in order to successfully make an incursion if they needed," he said.
In terms of deterrence, Breedlove said NATO has a good air and sea plan and is working in the next several days on developing a land component to that reassurance.
Ukraine is not a NATO member, but many countries that are members, such as Poland and the Baltic states, have voiced their increasing anxiety about Russia's recent actions.
NATO said on Tuesday that it would suspend "all practical civilian and military cooperation" with Russia in response to its annexation of Ukraine's southern Crimea region, which has triggered the worst East-West crisis since the Cold War.
It also said it had seen no sign that Moscow is withdrawing some of its troops from the eastern Ukrainian border, as Russia has claimed.
NATO chief Anders Fogh Rasmussen, speaking in Brussels at the conclusion of a two-day meeting of foreign ministers from the 28-member NATO bloc, said he shared Breedlove's concerns.
He accused Russia of trying to intimidate Ukraine as part of an attempt to "reestablish a Russian sphere of influence covering the former Soviet space."
Rasmussen again said Russia had a "massive military buildup along Ukraine's borders," with troops in a high state of readiness, and that NATO had not seen signs of any significant reduction in that buildup.
Urging Moscow to pull back its troops from the border, Rasmussen stressed that NATO wants to find a political and diplomatic solution to the crisis in Ukraine.
In an earlier media interview Wednesday, Breedlove said that Russia could "roll across the country in three to five days if it wanted to," a NATO military official said.