All three projects involve interceptors rockets designed to shoot down ballistic missiles in the terminal phase of their flight paths.
 
Republican proposal

The move was spearheaded by Duncan Hunter of California, the senior Republican senator on the House Armed Services Committee and a candidate for his party's 2008 presidential nomination.

It was a last-minute addition to the Democratic-controlled House's version of the fiscal 2008 defense authorization bill, which still awaits action in the Senate and reconciliation of any differences between the bills

Overall, the House included about $8.2bn for the Pentagon's Missile Defence Agency, a net reduction of $764m from the sum sought by George Bush, the US president.

The Missile Defence Advocacy Alliance, a lobbing group funded partly by companies involved in building missile shields, applauded the initiative to further integrate US and Israeli missile defences.