Darko Vojinovic, Associated Press
NATO Secretary General Jens Stoltenberg, listens to a question during a press conference, after talks with Serbian Prime Minister Aleksandar Vucic, unseen, in Belgrade, Serbia, Friday, Nov. 20, 2015. Stoltenberg arrived on a two-day official visit to Serbia.

BELGRADE, Serbia — Any attempt by Russia to interfere in Montenegro's bid to join NATO would only boost the country's chances of membership. The military alliance's secretary general said Friday

"The aspiration of Montenegro to become a member of NATO is something that is up to Montenegro and NATO to decide," Jens Stoltenberg said during a visit to Serbia.

"No one else has the right to intervene or to interfere with that decision," Stoltenberg added. "If any effect, Russian interference more likely will reinforce our interest to invite Montenegro to become a full member of the alliance."

NATO is expected to decide at a meeting on Dec. 1-2 whether to formally invite Montenegro to join. The United States has backed Montenegro's bid, but Russia — which has traditionally strong religious, cultural and historic influence in the Balkans — has been opposed, fueling anti-NATO sentiments among some Montenegrins. Several protests by thousands in Montenegro against the pro-NATO government recently have turned violent.

Anti-NATO sentiments are due partly to the Alliance's bombing campaign against Yugoslavia over Kosovo in 1999. Montenegro was part of Yugoslavia along with much-larger Serbia.

Stoltenberg said that "our air campaign in 1999 was never against the Serbian people" and expressed "deep regret" at the loss of innocent lives.

He added that NATO on Friday lifted all air restrictions in a central Serbian area bordering Kosovo that were imposed back in 1999. He described the decision as "a significant step toward full integration of the region into the European air space."