The Kremlin expressed concern on Monday over media reports that Poland has requested a permanent US military presence on its soil, saying NATO's expansion towards Russia's borders undermined stability in Europe.
Warsaw could offer up to $2 billion in funding for such a military presence, according to a Polish Defence Ministry proposal reported by Polish media.
A government source in Poland confirmed to Reuters such a proposal had been made. The Polish Defence Ministry did not immediately respond to a request for comment.
Asked about the move, Kremlin spokesman Dmitry Peskov said it was every country's sovereign right to take such decisions, but that it would harm the overall atmosphere on the continent.
"When we see the gradual expansion of NATO military structures towards our borders..., this of course in no way creates security and stability on the continent," Peskov told reporters on a conference call on Monday.
"On the contrary, these expansionist actions of course lead to counter-action from the Russian side in order to balance the parity which is violated every time in this way," Peskov said.
Poland joined NATO in 1999 along with Hungary and the Czech Republic, and since then many other former communist states - including the three Baltic republics bordering Russia - have joined in successive waves, despite Moscow's strong opposition.