Stationing heavy U.S. military equipment in the Baltic states and eastern Europe would amount to "the most aggressive step by the Pentagon and NATO" since the Cold War, Interfax news agency quoted a Russian Defense Ministry official as saying on Monday.

"Russia would be left with no other option but to boost its troops and forces on the western flank," General Yuri Yakubov was quoted as saying.

A U.S. official said at the weekend that Washington planned to store heavy military equipment in the Baltics and eastern Europe to reassure allies unnerved by Russia's role in Ukraine and to deter aggression.