ASTANA (Reuters) - Russia won the backing of China and other members of a regional security body in criticizing US plans for a missile shield, saying on Wednesday it could undermine global security. The Shanghai Cooperation Organization (SCO), a security bloc grouping Russia, China and four ex-Soviet Central Asian states, signed a declaration condemning any unilateral build-up of missile defenses after their leaders met in the Kazakh capital. "The unilateral and unlimited build-up of missile defense by a single state or by a narrow group of states could damage strategic stability and international security," the six members of the SCO said in the declaration. Apart from regional heavyweights China and Russia, the SCO also includes the mostly Muslim ex-Soviet Central Asian states of Kazakhstan, Kyrgyzstan, Tajikistan, and Uzbekistan. Iran, Pakistan, India and Mongolia have observer status in the body, set up 10 years ago to promote regional cooperation. Moscow has recently stepped up criticism of US plans to deploy missile defenses in Europe and has pressed for binding guarantees that the system would not weaken Russia's nuclear arsenal. Russian President Dmitry Medvedev has threatened a new Cold War-style arms race if Moscow and Washington fail to resolve the missile defense spat. Russian Foreign Minister Sergei Lavrov said SCO members had been unanimous in their criticism of the missile shield and that the declaration referred not only to the European system. "It is part of a global shield, and the global missile defense system being set up by the United States, which also covers East and South Asia," he said. The United States says its planned shield is meant to reduce the threat of a missile attack by Iran. Moscow says it fears the true aim is to neutralize Russia's own nuclear arsenal. "The Russian bear sits in its lair, and the NATO huntsman comes over to his house and asks him to come hunt the rabbit. .... Why do your rifles have the caliber to hunt the bear, not the rabbit?" Russia's NATO envoy Dmitry Rogozin said at a panel talk at London's Royal United Services Institute think-tank. US officials say the proposed shield could not neutralize Russia's vast arsenal, so Moscow has nothing to fear. "If we tried go in that direction it would not work, it would bankrupt us, it would not be in our interests and it is not going to happen," James Miller, US principal deputy under secretary of defense for policy, told the panel. Russia and China have often voiced unity in opposition to perceived US global dominance. As permanent members of the UN Security Council, they have expressed opposition to Western-led resolutions, including an effort to condemn Syria's bloody crackdown on anti-government protests. "The task of preserving global peace and promoting common development is getting more arduous and more onerous," Chinese President Hu Jintao said. Nevertheless, China and Russia have supported four rounds of UN sanctions against Iran over its nuclear program, effectively blocking full Iranian membership of the SCO when Tehran tried to join last year.