FACTBOX: Proposed U.S. missile shield in E.Europe

(Reuters) - The United States and the Czech Republic will sign a pact on Tuesday for the central European country to host a radar system, part of U.S. plans to create a missile defense shield in Europe.

The proposed shield, which also envisions up to 10 interceptor missiles in Poland, is meant to defend against what Washington says is the potential threat of a missile attack from Iran against European and U.S. targets.

The project needs approval in Poland and faces a tough parliamentary ratification process in the Czech Republic, where more than two thirds of the public oppose the plan. Russia is opposed to it and says it will threaten its security.

Following are some details about the proposed missile shield.

THE PERCEIVED THREAT

* General Henry Obering, head of the Pentagon's Missile Defense Agency (MDA), has said U.S. intelligence suggests that by 2015, Iran could follow North Korea's example and develop a long-range missile capable of striking the United Sates.

* The United States brought an earlier anti-missile umbrella, based in Alaska and California, on line in 2004 to protect against the perceived North Korean threat. The Czech and Polish sites would augment that system.

* Washington has tried to quell concerns in Moscow that the system would pose a threat to Russia by highlighting that the shield's missiles are defensive only -- carrying no warheads -- and would be no match for Russia's nuclear arsenal.

THE TECHNOLOGY