NATO announced on Monday it will deploy reconnaissance planes in Poland and Romania to monitor the crisis in neighboring Ukraine but the move looks unlikely to deter Russia from continuing to annex that country’s Crimea Peninsula.

The alliance said AWACS early warning aircraft, once designed to counter feared Soviet nuclear missile strikes, will start reconnaissance flights on Tuesday, flying from bases in Germany and the United Kingdom.

The United States, the most powerful country in NATO, earlier dispatched a warship to the Black Sea which it described as a “routine” deployment. The USS Truxton, a guided-missile destroyer, was due to conduct training exercises with naval forces from Bulgaria and Romania, two former Russian satellite states that joined NATO in 2004.

The deployment came a day after the United States put more F-15 fighter planes on air patrol missions in the Baltics in a bid to reassure the three former Soviet republics there. American president Barack Obama also spoke with the leaders of Estonia, Latvia and Lithuania by phone on Saturday.

The deployments did not appear to have an effect on Russia’s operations in the Crimea. Defying calls from Western powers to deescalate its intervention there, Russia expanded its military presence on the Black Sea peninsula over the weekend when Ukrainian army units were also mobilized across the country.

The European Union has threatened travel restrictions and asset freezes if Russia refuses to negotiate while the United States have warned of “costs.” But the Western countries are reluctant to step up pressure to the point where they might be drawn into open conflict with their former Cold War rival.

Russian troops entered the Crimea in late February after Ukraine’s elected president, Viktor Yanukovich, was deposed following months of protests against his decision to pull out of an associated agreement with the European Union in favor of deeper ties with his country’s former Soviet master, Russia. Russia has denied sending troops but President Vladimir Putin said last week he could use force as a “last resort” to protect Russian speakers and Russian interests in eastern Ukraine.

The Crimean regional parliament has formally requested annexation by Russia. A referendum to decide the region’s status, which Ukraine’s national government and Western allies say would be illegitimate, is expected to be held on Sunday.