Russia's invasion of neighboring Georgia has raised renewed questions over plans to extend North Atlantic Treaty Organization (NATO) membership to states that once formed  part of the former Soviet Union.  In April, NATO members agreed Georgia and Ukraine should become part of the alliance, and were set to discuss the matter further in December of this year. Moscow is staunchly opposed to the two countries joining NATO, and Russia's military offensive in Georgia has underscored the controversy of the NATO expansion issue. From Brussels, Nina Maria Potts filed this report for VOA narrated by Steve Mort.

For decades, NATO served to protect Europe from what was then the Soviet Union.  Then, after the collapse of the communist monolith almost 20 years ago, relations between Moscow and NATO improved.

Now Russia's decision to invade Georgia, a potential NATO member, has upset the alliance.

Alliance officials say relations between Moscow and NATO had begun to deteriorate even before the invasion occurred.

James Appathurai is the spokesman for NATO. "Our meetings have changed. They used to be a little bit more relaxed. We had a lot more in common than we had differences," Appathurai said. "Now there are some relatively frank discussions about things like NATO's enlargement, like Kosovo, like what's happening in Georgia, where NATO allies and Russia simply don't see eye to eye."

The enlargement of NATO has been a source of simmering tension between Russia and the West.  At a NATO summit in April, members agreed that Georgia and Ukraine should become part of the alliance.  

Russia strongly opposes such a move.   Russia's UN ambassador Vitaly Churkin emphasized this point at a news conference he called to discuss the Georgia crisis. "We have never made a secret of the fact that we think NATO enlargement is wrong and that with every new wave of enlargement, new security issues are created, and there are better ways to deal with matters of regional European, Euro-Atlantic security. More cooperative ways that would include, rather than exclude Russia," Churkin said.

Even before the Russian military move into Georgia earlier this month, Russian Ambassador to NATO, Dmitry Rogozin, was warning in interviews that an expansion of NATO to include nations bordering Russia would be unacceptable to Moscow.

"There are NATO-Ukrainian relations, there are NATO-Georgian relations, but there are also NATO-Russia relations," Rogozin said. "It's all about the balance of interests.  You have to take into consideration our point of view, and not approach a military machine close to our borders."

The expansion issue has highlighted divisions between NATO members over the consequences of bringing Georgia and Ukraine into the organization.  One controversial issue is whether NATO would be prepared to defend either country if they were members in future potential military conflicts with Russia.

Article five of the NATO treaty states that an attack on one member is an attack on all. While the U.S. has strongly supported membership for Georgia and Ukraine, France and Germany have been opposed.

Russian Ambassador Rogozin warns that an expansion of NATO, to include those countries, would jeopardize the status quo. "There would be real coldness in our relations. America and NATO would lose very important Russian support," Rogozin said.

Russian support already extends to some NATO operations in Afghanistan.  But some analysts say that the Afghanistan mission represents another serious long-term challenge for the alliance. There are some 53,000 NATO troops including support personnel in Afghanistan battling a Tailban resurgence there.

Nick Grono is from the International Crisis Group - a non-governmental organization involved in conflict prevention, says NATO troops did not secure southern Afghanistan soon enough. "And when we do send peacekeeping troops down there, not surprisingly, we find a very effective - a vigorous insurgency," Grono said.

Officials in NATO headquarters in Brussels say bringing stability to Afghanistan as well as the exansion of NATO to the east, are the two biggest challenges they face.  Both of those challenges, they say, would involve Russia.