NATO is a "mere instrument" of American foreign policy, Russian President Vladimir Putin has said in a series of interviews with film director Oliver Stone.

Axar.az reports citing Anadolu Agency.

In a trailer for The Putin Interviews, a documentary due to be aired June 12, Putin said countries joining NATO had become “vassals” of the U.S.

“Once a country becomes a NATO member, it is hard to resist the pressure of the U.S.,” Putin said. “And all of a sudden any weapon system can be placed in this country. An anti-ballistic missile system, new military bases and, if need be, new offensive systems.”

The interview was filmed months before Montenegro became the 29th member of the alliance on Monday. The former Yugoslav state has a cultural affinity to Russia through shared Slavic and Orthodox Christian roots. Russia condemned its accession as a “hostile course”.

Since the end of the Cold War, former Soviet satellites such as Poland, Hungary and Romania have joined NATO, as well as the three Baltic states that were once part of the Soviet Union.

Moscow has condemned NATO expansion while NATO has bolstered its eastern boundaries with troops, tanks and aircraft following Russia's 2014 annexation of Crimea and support for separatist militants in eastern Ukraine.

“We have to aim our missile systems at facilities that are threatening us,” Putin said. “The situation becomes more tense.”

He added: “Why are we so acutely responding to the expansion of NATO? Well, as a matter of fact, we understand the value, or lack thereof, and the threat of this organization.”

In the trailers, Putin warns that a war between the U.S. and Russia would result in a nuclear holocaust. “I don’t think anyone would survive such a conflict,” he said.