MOSCOW/WARSAW (Reuters) - A plan by Washington to station tanks and heavy weapons in NATO states on Russia's border would be the most aggressive U.S act since the Cold War, and Moscow would retaliate by beefing up its own forces, a Russian defense official said on Monday.  

The United States is offering to store military equipment on allies' territory in eastern Europe, a proposal aimed at reassuring governments worried that after the conflict in Ukraine, they could be the Kremlin's next target.

Poland and the Baltic states, where officials say privately they have been frustrated the NATO alliance has not taken more decisive steps to deter Russia, welcomed the decision by Washington to take the lead.

But others in the region were more cautious, fearing their countries could be caught in the middle of a new arms race between Russia and the United States.

"If heavy U.S military equipment, including tanks, artillery batteries and other equipment really does turn up in countries in eastern Europe and the Baltics, that will be the most aggressive step by the Pentagon and NATO since the Cold War," Russian defense ministry official General Yuri Yakubov said.