The U.S. announced Thursday the arrival of the 2nd Cavalry Regiment in a Polish NATO outpost located about 100 miles from Russia's militarized enclave of Kaliningrad. The troops are part of Washington's latest effort to bolster allied nation's against what they perceive to be a military threat from neighboring Russia. Moscow, however, has accused the U.S. and its NATO allies of undermining Russia's own security by surrounding it with hostile forces.

Vladimir Shamanov, head of the defense committee for Russia's lower house of parliament, said the country would consider adding more nuclear-capable Iskander ballistic missiles on its side of the border to deter a U.S. military buildup in the region.

"This creates prerequisites that may eventually enable them to create a certain stronghold. We will surely not turn a blind eye on this. We will take retaliatory measures," Shamanov said, according to the state-run Tass Russian News Agency.

"Not just personnel, but combat equipment. For instance, the group of Iskanders, including that in Kaliningrad, may be increased," he added.

The Russian Defense Ministry also weighed in Thursday, condemning the U.S. deployment and calling it a response to "unprecedented media hysteria" toward Moscow's massive Zapad-2017 military exercises held last month mostly in Belarus, Tass reported. A number of Western outlets speculated on how the large-scale Russian military mobilization may have permanent effects on the region, something Moscow denied.

Russian Defense Ministry spokesperson Igor Konashenkov said it was the U.S. "preparing for the aggression" by stationing the 2nd Cavalry Regiment across Russia's border without removing the military equipment of U.S. forces previously posted there, a move he said violated the 1997 NATO-Russia Founding Act. The agreement was designed to end decades of Cold War animosity between the two sides and states that "NATO and Russia do not consider each other as adversaries."

Since Russia annexed the Crimean Peninsula amid political unrest in neighboring Ukraine in 2014, however, NATO has significantly expanded its military presence near Russia, especially among the three Baltic states - Estonia, Latvia and Lithuania - and Poland. These four nations were designated by the U.S. last year to host NATO battle groups, but the multinational coalition has expanded its forces beyond these countries, drawing further Russian fury.

During a meeting Monday in Bucharest, NATO announced the formation of a 10-nation force in Romania, near the strategic Black Sea where both NATO and Russia have contended for influence. Romanian President Klaus Iohannis emphasized that the purpose of the deployment was "peace, not war," but Russia condemned the move as well as an "unacceptable and provocative" resolution adopted by the U.S.-led alliance censuring Russia for its actions in the Black Sea, according to state-run RIA Novosti.

U.S.-Russia relations declined drastically under the administration of former President Barack Obama and, after a brief respite following the election of President Donald Trump, have once again plunged. The White House and Kremlin have pledged to coordinate in defeating the Islamic State militant group (ISIS) in Syria, but both sides still have major grievances toward the other's global interests.