HUNTSVILLE — A Pentagon decision to defer certain work on a new high-speed missile interceptor to save money in the near term has driven up the program’s total cost by $1.5 billion, according to a Missile Defense Agency (MDA) official.

The MDA plans to modify Northrop Grumman’s contract for the Kinetic Energy Interceptor (KEI) this fall to cover the cost of deferring and stretching out the work, according to Carlton Brewer, MDA’s KEI program manager. This will increase the contract’s value to $6 billion, he said.

A second contract modification, worth $500 million, is expected to follow in 2007 to cover enhancements that will be designed to enable the KEI to intercept missiles in their midcourse phase, Brewer told reporters during an Aug. 16 briefing at the 2006 Space and Missile Defense Conference and Exhibition here.

The initial goal of the KEI program was to knock down missiles in their boost phase of flight, but the Pentagon decided last summer to add a midcourse intercept capability, Brewer said. MDA has completed concept studies on the midcourse capability, and the $500 million is intended to continue engineering work towards this goal, he said.

Northrop Grumman Mission Systems of Fair Lakes, Va., is the prime contractor for the KEI program, with Raytheon Missile Systems of Tucson, Ariz., as the primary subcontractor for the interceptor rocket.

The KEI program ended up absorbing most of the roughly $1 billion reduction to MDA’s 2006 budget request. As a result, the Pentagon deferred work on the program that was not directly related to a 2008 flight test. After that test, MDA is expected to choose between the KEI and another boost-phase system, the Airborne Laser.

In addition, the planned date for fielding KEI interceptors has moved from 2010 to 2014, Brewer said.

Funding prospects for the KEI effort in 2007 are uncertain. The MDA requested $406 million, but the Senate Appropriations Committee has recommended taking $200 million of that amount and applying it toward more near-term efforts such as the Ground-Based Midcourse Defense System. The House version of the Defense Appropriations Act of 2007 recommends fully funding the KEI program, leaving the matter to be resolved in conference. Brewer said that MDA hopes to flight test KEI around 2010 or 2011.

The agency also is looking at options for placing the system on Navy ships, which could enable the interceptors to be moved around the world to fire from more optimal locations, and could conduct a flight test of the rocket from a ship at some point after the first ground-based flight test, Brewer said.

MDA is currently looking at options for ships that include Navy cruisers, destroyers and submarines, as well as systems based on commercial container vessels, Brewer said.

Chuck Ross, Raytheon vice president for KEI, said during an Aug. 15 briefing with reporters that the design for the ground-based KEI interceptors are fired using a “cold case eject” that uses a technique like steam pressure to shoot the rocket out of its tube, rather than having the rocket’s first stage ignite while still inside the firing tube.

This method will translate well to a sea-based firing system because it prevents the deck of the ship from being exposed to the heat and energy of the rocket’s exhaust plume, he said.

The next milestone for the KEI system is a firing of the rocket’s first stage that will take place this fall to ensure that the system is generating sufficient thrust and burn time, Brewer said. Previous testing this year has included a firing of the rocket’s second stage in January, and a demonstration in March that tested the ability of a deployed KEI battery to receive targeting from multiple satellite constellations.