WASHINGTON: The Pentagon is redirecting its missile defense efforts by winding down multibillion-dollar programs aimed at destroying enemy missiles very soon after they take off.

The move away from "boost-phase" intercept programs was announced as part of President Barack Obama's fiscal 2010 budget request sent to Congress on Thursday.

The Pentagon's Missile Defense Agency said it had turned bullish in recent months on prospects for intercepts during the ascent phase, which it termed "significantly less challenging".