UPDATE 2-Pentagon eyes new anti-missile technology

* Boost-phase efforts being dropped

* Pentagon eyes new "ascent phase" technology

* Funding up for Aegis, THAAD programs (Recasts with information from Pentagon briefing)

By Jim Wolf

WASHINGTON, May 7 (Reuters) - 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."

The ascent phase starts after powered flight, but before a ballistic missile deploys decoys or executes maneuvers to avoid being shot down in the post-boost phase of its flight.

"We believe technologies now available -- not previously available -- make this a more suitable, more affordable enterprise," said retired Navy Rear Admiral David Altwegg, the agency's executive director.