The North Atlantic Treaty Organization (NATO) has failed to keep its non-expansion "promise," but there should be no war, said Russia's Security Council Deputy Chairman Dmitry Medvedev on Thursday.
"They promised not to expand NATO, but didn’t keep the promise," Medvedev said, according to state news agency TASS.
"They say that ‘we did not sign anything.’ But we all know well who and when granted to whom such promises, such assurances," he added.
"Did they promise not to expand, let’s say, on the territory of the former Soviet Union? They promised it either in this way or another in private talks," said Medvedev.
"They failed to keep all their promises. They are now encroaching on our state borders," he added.
"There must be no war in any way, nobody is looking to start the war, and everything must be done to avoid any war. Moreover, on behalf of Russia and supposedly the North Atlantic alliance," he said.
Medvedev also added that a war would be "horrifying" and there are people who make money by raising tensions.
A process of negotiations on security guarantees is the only way to settle the current tensions between Russia, Ukraine and the West, he added.
Medvedev's remarks go directly against one of NATO's key principles, enshrined in its founding document. Since its inception, the alliance has had an "open-door policy." This says that any European state that is ready and willing to undertake the commitments and obligations of membership, and whose membership contributes to security in the Euro-Atlantic area, is welcomed to apply. Any decisions on enlargement must be agreed unanimously.
At a summit in Brussels in 1994 NATO leaders made it clear that they would welcome expansion to the east, and in 1997, the Czech Republic, Hungary and Poland were invited to begin accession talks.
Russia has made similar claims about NATO before, and the US and NATO have rejected them in the past.