NATO's deputy chief says Montenegro's membership in the Western military alliance is progressing smoothly despite strong opposition from Russia.

NATO Deputy Secretary-General Rose Gottemoeller says that she expects that the tiny Balkan country will become a member in spring 2017 after all 28 NATO member states and Montenegro ratify the agreement in their parliaments.

Gottemoeller said Thursday in Montenegro that "I think your membership in NATO is moving forward smoothly."

Montenegro has been invited to join NATO despite strong opposition from its traditional Slavic ally Russia.

Montenegrin officials have accused Russia of standing behind an alleged coup on election day in October to topple the pro-Western government because of its NATO bid.