FACTBOX: Details on new U.S. approach to missile defense

(Reuters) - U.S. President Barack Obama said on Thursday the United States would take a new approach to missile defense, replacing plans of predecessor George W. Bush to set up a shield against long-range missiles in Eastern Europe.

Below are facts about the new approach, according to the White House and briefings by U.S. officials:

OVERVIEW

The new approach is based on an updated assessment of the missile threat posed by Iran and a commitment to use cost-effective and proven technology, the White House said.

NEAR TERM FOCUS

Starting around 2011 the new system will include sea- and land-based missile interceptors and sensors in Europe.

It is designed to offer "more effective defenses against more near-term ballistic missile threats," the White House said, while increasing current protection of the United States against long-range ballistic missile threats.

U.S. allies and personnel stationed in the Middle East and Europe face the greatest missile threats from Iran, it said.

REASONS FOR THE CHANGE

Intelligence reports show that the threat of Iran's short- and medium-range ballistic missiles is accelerating faster than first projected while the threat of longer range missiles was not moving as quickly as first estimated.

The changes take into account advancements in U.S. missile defense technologies.

PHASED TIMELINE

The plan lays out a four-phase timeline from 2011 to 2020 for deployment of missile systems, starting with those that address regional ballistic threats to Europe and ending with those that would target medium and intermediate-range missiles and the threat of intercontinental ballistic missiles to the United States.

POLAND AND THE CZECH REPUBLIC

New missile interceptor and sensor architecture would not require one large fixed European radar that was originally planned to be based in the Czech Republic.

The new technology also eliminates the need for a field of 10 ground-based interceptors in Poland.

The original system would have deployed a radar in the Czech Republic that was omnidirectional and concerned Moscow because it could have looked deep into Russia.

The radar proposed for the new system is single-directional and the No. 2 U.S. military official, General James Cartwright, said, "It'll be very clear that it is pointing south toward Iran."

The new radar is more likely to be deployed somewhere in the Caucasus than in the Czech Republic.

U.S. officials stressed that Poland and the Czech Republic were close U.S. allies who would be central to NATO consultations on defense against ballistic missiles going forward.

RUSSIA

White House spokesman Robert Gibbs said the change did not involve a quid pro quo with Russia, which opposed the original Bush-era proposals.

The United States would welcome Russia bringing "its missile defense capabilities into a broader defense of our common strategic interests."

The United States would like to see Moscow incorporate its Armavir radar in the southern part of Russia into the radar network.

(Reporting by Jeff Mason and Phil Stewart in Washington)