* U.S.'s Kerry to tour all five states in central Asia

* Visit signals U.S. wants to maintain its influence

* Moscow concerned about militants infiltrating region

By Dmitry Solovyov and Matt Spetalnick

ALMATY/VIENNA, Oct 30 (Reuters) - After Ukraine and Syria, the ex-Soviet republics of central Asia could become the latest venue for geo-political rivalry between Moscow and Washington, driven by Kremlin worries about Islamists and U.S. suspicion about Russia's true intentions.

U.S. Secretary of State John Kerry is due to tour all five states in central Asia, in a signal the United States wants to maintain its influence, even though it is drawing down its troop presence in nearby Afghanistan.

His visit coincides with a chorus of warnings from Russian officials about the danger of Islamic State militants infiltrating the region from Afghanistan, accompanied by hints Moscow will respond by beefing up its military presence.

Though Russian officials say they are driven only by concern about militants, not geo-political rivalry, their heightened attention risks fuelling U.S. suspicions that Moscow is trying to rebuild its old empire.

"It's about, if you will, a sort of neo-imperial vision for how the world works, and it's connected to Russia's larger geopolitical ambitions," said Jeffrey Mankoff, Deputy Director and Senior Fellow at Washington think tank CSIS.

ANXIETY OVERSTATED

A senior U.S. official briefing reporters before Kerry's trip said the visit was not about making the region's governments choose between world powers, or trying to displace Russian influence.

The trip was intended to reassure partners in central Asia that the withdrawal from Afghanistan did not mean waning U.S. interest in their security and economic needs, said the official, speaking on condition of anonymity.

But the official said that Russia has been exaggerating the sense of insecurity in the region about Islamist militants.

"The anxiety levels in the region are probably higher than the actual level of activity would warrant," the official said.

Since the Sept. 11, 2001 attacks on U.S. cities and the subsequent U.S. invasion of Afghanistan, Moscow and Washington have been observing an uneasy truce over central Asia.

Moscow maintained its influence there, with troops helping Tajikistan guard its borders for several years and military bases in Tajikistan and Kyrgyzstan.

At the same time it acquiesced when the United States established its own air bases in Uzbekistan and Kyrgyzstan and used the region to re-supply its operations in Afghanistan.

That relationship was thrown out of equilibrium by a resurgence in activity by Islamist militants in Afghanistan and the drawdown of U.S. troops in Afghanistan.

The Taliban takeover of the city of Kunduz, in northern Afghanistan near the border with ex-Soviet Tajikistan, alarmed officials in Moscow. They fear Islamist militants could use central Asia as a bridgehead into Russia.

"We have Afghanistan ... and all that is linked and the Tajiks are barely managing, and if the Tajiks cannot manage then it will come to Russia next," said a Russian government official who spoke on condition of anonymity.

In the past few months, Moscow has sent extra aircraft to its air base in Tajikistan, and the Moscow-dominated ex-Soviet grouping, the Commonwealth of Independent States, announced the creation of a joint border force that could go to the Tajik-Afghan border.

ISOLATING MOSCOW

Kerry's visit is the first time that a U.S. Secretary of State have visited all five ex-Soviet republics in succession on a single trip.

Kazakhstan, Kyrgyzstan and Tajikistan are firmly within Moscow's orbit, but Turkmenistan and Uzbekistan, both run by rulers who brook no dissent, are more independent-minded and could be courted by the United States.

"Kerry will attempt to isolate Moscow," said Temir Sariyev, an analyst based in Kyrgyzstan, where Kerry will start his tour. "Not all Central Asian nations back Russia."

Visiting the Turkmen capital Ashgabat, Kerry is likely to bless a U.S.-backed project aiming to bring Turkmen natural gas to Pakistan and India via Afghanistan. The route will reduce Turkmenistan's reliance on Russia to buy its output.

In the blue-domed Uzbek city of Samarkand, once a central point on the Silk Road and the 14th century capital of conqueror Tamerlane's empire, Kerry will hold a meeting with foreign ministers of the five central Asian states.

Uzbekistan and Turkmenistan are listed by human rights bodies among the world's most repressive and isolated regimes. Kerry will raise U.S. concerns about human rights at his meetings, the U.S. official said.

But Kerry will also focus on the need to build stronger relations with states in the region.

"It looks like Washington is trying to reincarnate its old project of creating some kind of regional unity of the five nations within 'Greater Central Asia', beyond their ties with Russia and China," said Alexander Knyazev, a Kazakhstan-based Central Asia expert. (Writing by Christian Lowe; editing by Susan Thomas)

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