NATO’s Jaap de Hoop Scheffer said the 28-nation alliance was not in competition for the region, in what was seen as a veiled reference to Russia which regards the ex-Soviet states as in its sphere of influence.

"NATO is not competing with anyone ...there are other nations and organisations involved in this region and let the nations in this region decide for themselves what kind of a relationship they want (with NATO)," he told reporters in the Kazakh capital.

"I think Kazakhstan and other nations are interested in having a relationship with NATO and how far they want to go is up to them," he said after talks at the Euro-Atlantic Partnership Council.

The talks in Kazakhstan are taking place days after ex-Soviet republic Kyrgyzstan reversed its decision to shut down a US military air base used to support operations in Afghanistan.

Kazakhstan, Tajikistan and Uzbekistan, together with Russia, make up a corridor along which the United States plans to supply its troops in Afghanistan following attacks on convoys in Pakistan.

But De Hoop Scheffer ruled out any extension of NATO’s role from Afghanistan into neighbouring countries.

"NATO’s mandate ends at the borders of Afghanistan", he said.

Central Asian countries are not NATO members but some are linked to Russia through multilateral security organisations such as the Shanghai Cooperation Organisation and the Collective Security Treaty Organisation.

Central Asia has gained significance for Washington as it boosts its Afghan force to fight the resurgent Taliban.

"Instability in Afghanistan affects Central Asia more than any other region; from terrorism to drug-trafficking," De Hoop Scheffer said at a lecture to the Kazakh Academy of State.

"By the same token, no region has more to gain from stability in Afghanistan than Central Asia," he said.

Earlier this week, Kyrgyzstan said its security service officers fought and killed five Islamist militants from a group long linked to Afghanistan’s Taliban.

Kyrgyz Foreign Minister Kadyrbek Sarbayev said on Thursday there was a growing threat to the region from extremism and that the Islamic Movement of Uzbekistan (IMU) was moving militants into the region.

"They have started returning to Central Asia. We must think about our country now and our national interests," Sarbayev told lawmakers.