The West is worried about risks to stability in the vast Muslim region, dominated by authoritarian but secular governments. Analysts believe Islamist militancy could spread into the heart of Central Asia from nearby Afghanistan.
US Special Representative for Afghanistan and Pakistan Richard Holbrooke is on a blitz tour of the five "stans" of Central Asia.
"I think the real threat in this region is less from the Taleban but from Al-Qaeda, which trains international terrorists," he said on a visit to Tajikistan.
"This is an issue of common concern to the United States and to all the countries of this region. And by all the countries I definitely include Pakistan and China and India." Stability in the vast resource-rich region sprawling between China, Russia and Afghanistan is crucial to the West as it lies on a new supply route for NATO-led operations in Afghanistan.
The Islamic Movement of Uzbekistan (IMU) wants to topple Central Asia's secular post-Soviet leaders and establish Islamic rule.
Its fighters were forced out of the region after the end of a 1990s civil war in Tajikistan into Pakistan's lawless tribal areas, where its leadership is believed to have established close contacts with Al-Qaeda, security analysts say.
IMU fighters are now believed to be returning to Central Asia to seed unrest in a region weakened by a protracted economic crisis and people's frustration with growing poverty.
Holbrooke is also visiting Kyrgyzstan, Uzbekistan, Turkmenistan and Kazakhstan during his first trip to Central Asia in his current capacity.
In Uzbekistan, the region's most populous and ethnically diverse nation, President Islam Karimov told Holbrooke he was eager to work closer with the United States over Afghanistan.
"The leader of our nation ... expressed Uzbekistan's firm determination to further develop US-Uzbek relations in a constructive way in light of efforts to bring lasting peace and stability to Afghanistan," the official UzA news agency said.
Relations between Uzbekistan, long under fire over human rights violations, and the United States have improved in recent years as Washington has shifted focus more to security issues in its contacts with Tashkent, diplomats say.
Uzbekistan is now part of the new NATO supply route and Western nations rarely criticize its rights record. Last year the European Union angered international human rights groups by lifting sanctions it imposed on Uzbekistan after a violent crackdown by Uzbek troops on protesters in 2005.
