BRUSSELS - NATO Secretary General Jens Stoltenberg said Wednesday the alliance will not get dragged into an arms race with Russia but must counter Moscow's "aggressive actions" in Ukraine.
Defence ministers are due to approve measures including the more than doubling of NATO's rapid response force, while the US on Tuesday announced it would pre-position heavy weapons on the alliance's eastern flank.
"We will not be dragged into an arms race but we must keep our countries safe," Stoltenberg said as the meeting opened at NATO HQ in Brussels.
"What Russia has done in Ukraine is not defensive; to annex (Crimea) ... that is an act of aggression."
Stoltenberg played down fears of a return to the worst days of the Cold War, insisting that was not the case and that NATO's response was "defensive, proportionate and in line with all our international obligations".
"Russia continues to send troops, forces and supplies into eastern Ukraine. There is no doubt that Russia is responsible for aggressive actions in Europe," he said.
Since the Ukraine crisis erupted NATO has adopted a series of measures to give it a very high-speed reaction unit, on top of a fast response force which will be increased to some 40,000 troops from 13,000 to meet the Russian challenge.
US Defence Secretary Ashton Carter announced Tuesday that Washington would pre-position heavy weapons in central and eastern Europe to ensure any NATO troops responding to a fresh crisis will hit the ground running.
"While we do not seek a cold, let alone a hot war with Russia, we will defend our allies," said Carter, who will be attending his first NATO defence ministers' meeting.