"The summit in Madrid confirms and consolidates this bloc's policy of aggressive containment of Russia," Deputy Foreign Minister Sergei Ryabkov said, Russian news agencies reported.

"We consider the expansion of the North Atlantic alliance to be a purely destabilising factor in international affairs."

NATO leaders were set Wednesday to invite Finland and Sweden to join after Turkey dropped objections, as the alliance looked to revamp its defences at a summit dominated by Moscow's intervention in Ukraine.

More than four months after Russia sent troops to Ukraine, upending the European security landscape, leaders gather in Madrid for what NATO chief Jens Stoltenberg called a "historic and transformative summit" for the alliance's future.

Ryabkov said Russia knew what to expect from the summit.

"A new strategic concept will be adopted, where Russia is going to be called a threat to the alliance," he said.

"This has nothing to do with real life. It is the alliance that poses a threat to us."