Montenegrin President Filip Vujanovic (right) talks with U.S. Senator John McCain (left) during their meeting in Podgorica on April 12, 2017, a day after President Donald Trump signed off on Montenegro's accession to NATO | Savo Prelevic/AFP via Getty Images Russia protests US approval of Montenegro’s NATO membership The foreign ministry warned that Montenegro’s accession would cause further divisions in Europe.

The U.S.'s decision to green-light Montenegro's application to join NATO was "deeply mistaken" and would create further division in Europe, the Russian foreign ministry said Thursday, AFP reported.

"We consider the course towards including Montenegro in NATO is deeply erroneous, goes fundamentally against the interests of people in this country and harms stability in the Balkans and in Europe as a whole," it said in a statement.

The Russians added that "puppet NGOs" helped the Balkan country's accession by creating "the illusion of public support."

U.S. President Donald Trump signed off on Montenegro's accession to the military alliance on Tuesday.

The Kremlin has long considered the country to be under its sphere of influence. Russia was accused of being behind an attempted coup in Montenegro during an election in October last year.

Montenegro hopes to become a member of the alliance later this year.