WASHINGTON (CNN) -- President Bush has decided to deploy a limited system designed to protect the United States against a ballistic missile attack, with the first phase of the controversial system scheduled to be deployed within two years, senior administration officials tell CNN.

Bush planned a written statement Tuesday announcing his decision, and Pentagon officials were to address the scope of the plan and its technological capabilities later in the day. Great Britain said it has been asked by the United States to upgrade some early warning radar system.

Bush made missile defense a key promise of his 2000 campaign, and early in his administration was sharply criticized by many Democrats; Russia, China and several European allies for pushing to withdraw from the Anti-Ballistic Missile Treaty of 1972 so he could pursue the program.

But ultimately, an accord was reached with Russia on the ABM treaty, and the international criticism quieted considerably, although China still is critical. Withdrawing from the ABM was a critical step because the treaty specifically prohibited testing and deployment of missile-defense systems.

Star Wars defense
The goal of a missile defense shield dates back to the Reagan administration, where the program was labeled by some as Star Wars and at times involved talk of space-based systems.

Bush has settled, at least for now, on a more limited system that includes deployment of ground-based interceptor missiles -- beginning at Fort Greeley, Alaska. Preliminary work on that site began earlier in the administration, and the officials say the plan to be announced by Bush calls for the first battery of interceptors to be deployed by 2004, with an additional battery to be in place within a year or two of that.

Those interceptors are designed to destroy any long-range missiles fired at the United States, or conceivably at a U.S. ally.

A system designed to destroy short-range and medium-range missiles would be deployed as well aboard Aegis class Navy ships. Aegis is an advanced radar and battle management system.

China has been critical of any deployment of U.S. warships in Asia with missile-defense capabilities. It has been even more critical of discussion in the United States about selling Aegis class warships to Taiwan and possibly including Taiwan in a missile defense program.

The United States has not approved such a sale to Taiwan, but has said it would consider it down the road depending on the political and military situation.

flak，你說的那個三節的玩具是這個嗎？連RFP都還沒開始的新泛用型飛彈: