NATO on Thursday said parliamentary polls in Georgia next month would be a "litmus test" for its democratic credentials amid rising tensions between governing party and opposition.

"The conduct and the run-up to parliamentary elections this October and presidential elections in 2013 will be a litmus test for Georgian democracy," NATO Secretary-General Anders Fogh Rasmussen told a news conference during a visit to Tbilisi.

The governing party of President Mikheil Saakashvili is facing its toughest electoral battle since coming to power after the 2003 Rose Revolution, against a revitalised opposition led by billionaire tycoon Bidzina Ivanishvili.

Saakashvili told the news conference that Georgia would "continue its democratic path".

"On October 1, we will hold the most free, most transparent elections... in the history of independent Georgia," he promised.

Rasmussen said that the reforms undertaken by Saakashvili's Western-backed government had taken the ex-Soviet state closer to its goal of NATO membership.

"The future is in your hands but know that you have a friend in NATO and a future home in NATO," he said.

NATO leaders agreed at their 2008 summit that Georgia could join at an unspecified point in the future, although they were denied coveted pre-membership status amid strong opposition from Russia.

The small Caucasus state's aspirations to join NATO have infuriated powerful neighbour Russia, which fought a brief war with Georgia in 2008 and does not want the Western alliance to expand further eastwards.

Seeking to prove itself as a reliable partner, Georgia has become the second largest non-member contributor to NATO's mission in Afghanistan, deploying 800 troops to help combat the Taliban and suffering 17 losses so far.