Russia says a new US military deployment to Poland announced by President Donald Trump on Wednesday would force Moscow to take retaliatory steps.
Trump told Polish President Andrzej Duda on Wednesday that he had decided to send an additional 1,000 troops to Poland to join 4,000 forces already there.
The US will also send a squadron of MQ-9 Reaper Intelligence, Surveillance, and Reconnaissance drones as well, he added.
The announcement drew response from Russia, which said on Thursday that “its military is tracking these announcements very closely.”
Kremlin spokesman Dmitry Peskov said Moscow “is analyzing the information, and is doing what is necessary so that such steps in no way threaten the Russian Federation's security.”
Sergei Ryabkov, a Russian deputy foreign minister, said Trump's move probably reflected "aggressive" intentions.
Russia's foreign ministry described Trump’s decision for more deployment as a betrayal of Russia's core agreement with the North Atlantic Treaty Organization (NATO) in 1997.
Under the deal, NATO had agreed not to permanently deploy significant military forces on the territory of new member states.
"The headquarters structures that will be set up in Poland under this reinforcement will deliver much greater potential,” the Russian ministry said in a statement.
Russia, it said, could not “fail to take this into account in its defense planning and practical activities.”
“We see in this signs of preparation for further large-scale deployments," it added.
Russian parliamentarians separately reacted to the decision, with one lawmaker threatening to make Poland a target in the event of a military conflict.
"In the event of any conflict, God forbid, the territory of Poland would become a clear target for a retaliatory strike, if there was suddenly an attack on us," said Vladimir Dzhabarov, deputy head of the upper house of parliament's international affairs committee.
Another lawmaker, Vladimir Shamanov, raised concern that the US drones could be capable of carrying nuclear weapons at some point, warning that this would gradually lead the world “towards a dangerous moment.”
Russia has formerly warned that any increased military presence in Poland could prompt it to step up its military presence in neighboring Belarus.
UK forces tasked to focus on Russia
Meanwhile, UK forces will be shifting away from counter-terrorism work and instead concentrate on blocking what British military describes as covert operations by countries such as Russia.
Citing unnamed British officials and military sources, a BBC report said on Thursday that “the need to confront dangerous international behavior by peer adversaries is increasing."
"Under the new plan, an operation might be mounted in a Baltic republic or African country in order to uncover and pinpoint Russian covert activities," the report said.
Relations between the UK and Russia hit a new low last year, after London accused Moscow of ordering a poison attack on Sergei Skripal, a former double spy, and his daughter in Salisbury in southern England last year.
Russia has repeatedly denied any involvement in the alleged attack which left the former Russian spy unconscious for weeks. President Putin also said the Skripals case benefited London more than Moscow.