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

(Reuters) - Polish Defense Minister Bogdan Klich met on Tuesday with Defense Secretary Robert Gates to discuss Poland's prospective role in a controversial U.S. plan to erect a missile defense system in Eastern Europe.

Here are some facts about the proposed missile shield:

* The system known to the Pentagon as the Ballistic Missile Defense European Capability is intended to protect Europe and the United States against a limited intermediate- and long-range ballistic missile attack from the Middle East. It would augment an existing anti-missile umbrella based in Alaska and California;

* The proposed $3.5 billion system would use "hit-to-kill" technology that operates without explosives. An array of sensors and radar would detect a missile in flight. A ground-based interceptor would then be launched to ram the incoming warhead at a closing speed of 15,000 miles per hour (24,000 kph);

* Washington has proposed placing as many as 10 interceptor missiles with a range of up to 1,800 miles in Poland. The missiles would be housed in underground silos in an area about the size of a football field;

* U.S. officials also proposed a radar installation for the Czech Republic. The facility would aim its radar beam at the Middle East to detect a missile threat in flight and guide interceptor missiles into the trajectory of the approaching warhead;

* If Washington can secure agreements with Poland and the Czech Republic, site construction could begin in 2009. U.S. defense officials say the European system could be fully operational by 2013.

(Reporting by David Morgan; Editing by Kristin Roberts)