NATO says it is deploying reconnaissance aircraft along the borders of member states Poland and Romania, to monitor the crisis in nearby Ukraine.
The Western military alliance said the decision to send AWACS (Airborne Warning and Control Systems) surveillance planes was made on Monday, with the approval of the 28 members. It said the deployment is designed "to enhance the alliance's situational awareness."
Last week, NATO said it was launching a review of all military cooperation with Russia, in response to what witnesses describe as a massive Russian military incursion into Ukraine's Crimean peninsula.
U.S. Defense Secretary Chuck Hagel also announced a new deployment of U.S. fighter jets to patrol Estonia, Lithuania and Latvia -- the three allied Baltic nations sharing a border with Russia. Additionally, a U.S. Navy guided missile destroyer is set to begin Black Sea maneuvers with Romanian and Bulgarian warships in the coming days.
Moscow has officially denied that its troops are participating in the Crimean occupation. But witnesses say military personnel in unmarked uniforms arrived in Russian-registered vehicles earlier this month and freely admit to to being Russian.