NATO offered membership to Montenegro, extending its reach deeper into southeastern Europe and potentially adding to tensions with Russia.
The 28-nation U.S.-led military alliance agreed to start the entry process at a meeting of foreign ministers in Brussels on Wednesday, Secretary-General Jens Stoltenberg said. Full membership for the former Yugoslav republic could take up to two years.
This is a "historic decision" and affirms NATO's "open-door policy," Stoltenberg said.
Russia has opposed, but has been powerless to prevent, North Atlantic Treaty Organization expansion into eastern European countries that were under Soviet domination during the Cold War. While Montenegro, with 620,000 people, was never a Soviet satellite, it maintains strong economic ties with Russia.