MOSCOW (AP) – Uzbekistan has suspended its participation in a Russia-dominated security pact of ex-Soviet nations, officials said Thursday, a move that reflected tensions inside the grouping.

The Collective Security Treaty Organization’s spokesman, Vladimir Zainetdinov, said Thursday that it received a note from Uzbekistan declaring the suspension of its involvement in the seven-nation alliance. Zainetdinov wouldn’t comment on possible motives behind the move, and Uzbek officials couldn’t be reached for comment. The grouping also includes Russia, Armenia, Belarus, Kazakhstan, Kyrgyzstan and Tajikistan.

Russia has touted the CSTO as an ex-Soviet response to NATO, but the pact has remained amorphous and weakened by differences among its members. The pact members created a joint rapid reaction force that held sporadic maneuvers, but its numbers were small and its mission unclear. Uzbekistan has refrained from contributing its troops to the force in an apparent reluctance to give Russia too much clout.

Uzbekistan left the grouping once before in 1999, but returned in 2006, reflecting its strongman ruler’s often unpredictable decisions.

Uzbek President Islam Karimov was the country’s Communist Party boss and stayed at its helm after the 1991 Soviet collapse. He has ruled the resource-rich, strategically-placed Central Asian nation of 27 million with an iron fist, tolerating no dissent. International rights groups list Uzbekistan among the world’s most corrupt and repressive nations.

Over the past two decades, the 74-year old Karimov has maneuvered between Russia and the West, periodically shifting loyalties.

Karimov allowed the United States to use a major air base for the war in Afghanistan after the September 11, 2001, terror attacks, but he fell out with the U.S. and other Western nations after violently cracking down on a 2005 uprising in the city of Andijan and moved to boost ties with Moscow. In recent years, Karimov has sought to mend ties with the West while Uzbekistan’s relations with Russia have grown colder.

Vladimir Zharikhin, a Moscow-based political expert studying the ex-Soviet nations, told the RIA Novosti news agency that Uzbekistan’s decision had been prompted by “Karimov’s intention to flirt with the U.S.” He added that the Uzbek leader later may again lurch in the opposite direction.

Also under Karimov, Uzbekistan’s ties with its Central Asian neighbors often have been strained amid a series of disputes over borders and water-sharing.

In Tajikistan, head of the parliamentary defense committee Amirkul Azimov criticized Uzbekistan’s move.

“Uzbekistan’s decision doesn’t help collective security in the region,” he was quoted as saying by RIA Novosti.

Azimov said that the planned withdrawal of NATO forces from Afghanistan would leave a “hornet’s nest” threatening Central Asia.

Nikolai Fedoryak, a deputy chief of the defense and security committee in the upper house of the Russian parliament, also said that Uzbekistan may regret its decision after U.S. and other forces leave Afghanistan as scheduled by the end of 2014.

“It’s regrettable that Uzbekistan made that move without a thorough analysis of its consequences,” he told the Interfax news agency.

(Copyright 2012 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.)

Follow @KTAR923