Moscow on Sunday slammed NATO for focusing on a "non-existent" threat from Russia at a leaders summit in Warsaw that saw fears over the Kremlin's expansionism high on the agenda.

"A preliminary analysis of the results of the meeting shows that NATO continues to exist in some sort of military-political looking-glass world," the foreign ministry said in a statement.

"Contrary to the objective interests of maintaining peace and stability in Europe... the alliance concentrates its efforts on deterring a non-existent threat from the East," the statement said.

NATO leaders united in Warsaw Saturday behind a "hard-headed" policy of deterrence and dialogue with Russia after launching the alliance's biggest military revamp since the Cold War to counter a resurgent Moscow.

Alliance chief Jens Stoltenberg said alliance leaders "stand together" on Russia, agreeing at a summit in Warsaw to bolster its eastern flank after Moscow's annexation of Crimea and the Ukraine conflict.

Russian President Vladimir Putin has opposed NATO's decision to put four battalions in Poland and the Baltic states, seeing the expansion into Moscow's Soviet-era backyard as a direct security threat.

"The alliance is united, we stand together," Stoltenberg said when asked about the leaders' talks on Russia.

"The united message is that defence and dialogue are what our relationship is based on."

NATO will hold fresh talks with Russia on July 13 in Brussels just days after the landmark alliance summit.