U.S. President Donald Trump (R) and visiting NATO Secretary General Jens Stoltenberg attend a joint press conference in Washington D.C., the United States, on April 12, 2017. (Xinhua/Yin Bogu)

MOSCOW, April 13 (Xinhua) -- Montenegro's upcoming accession to the North Atlantic Treaty Organization (NATO) will harm stability in the Balkans and in Europe as a whole, Russia's Foreign Ministry said on Thursday.

"We consider this step as a manifestation of inertia in Washington's policy, reflecting the logic of confrontation on the European continent, creating new dividing lines," the Foreign Ministry said in a statement.

On Tuesday, U.S. President Donald Trump signed a protocol to ratify Montenegro's accession to NATO, and the Balkan country will officially join the alliance as its 29th member next month in Brussels.

Montenegro's accession to NATO is not based on real public opinion and has incurred criticism even in the United States, the statement added.

Tensions between NATO and Russia have escalated as both are engaged in military build-up along the Russian border. Moscow strongly opposes the bloc's eastward expansion, which it says threatens its national security.