The Kremlin expressed alarm Thursday over the arrival of U.S. troops in Poland, claiming military exercises are “destabilizing” security in the region, the BBC reported. More than 3,000 U.S. soldiers have been deployed to Poland to conduct military exercises as part of Operation Atlantic Resolve, a plan by the Obama administration to reassure NATO allies of the U.S. commitment as Russia flexes its muscles in Ukraine. The latest phase of the operation, kicking off just days before Donald Trump takes office, has been met with indignation in the Kremlin. Kremlin spokesman Dmitry Peskov told the BBC on Thursday that the move “threatens our interests and our security.” “It’s a third country that is building up its military presence on our borders in Europe. It isn’t even a European country,” he said. Alexei Mechkov, Russia’s deputy foreign minister, said the drills are “destabilizing European security.” Poland has defended the drills, saying it’s necessary in light of Russia’s aggression in the region.