Defense Secretary Donald H. Rumsfeld has decided to fund a fourth of six new medium-weight Army combat brigades in the fiscal 2004 budget, but to defer a decision on the final two units until July in hopes of increasing their firepower, a senior defense official said yesterday.

The decision affirmed the value of the Army's so-called Stryker Brigade Combat Teams, the centerpiece of the Army's efforts to move from heavy, armored units to a more rapidly deployable force. But it left the fate of the final two brigade combat teams uncertain.

Briefing reporters, the official described the new brigades as valuable but incomplete additions to the future battlefield, and said a decision on whether to fund the final two will come only after officials look at possibly adding attack helicopters, 155mm howitzers and reconnaissance drones to increase their firepower and command capabilities.

One alternative to funding the fifth and sixth units, at a cost of about $1.5 billion each, the official said, would be to go back and reequip the first three brigades for greater combat "punch."

The units are named after a new eight-wheeled combat vehicle called the Stryker that comes in 10 variants, from troop carriers to mobile 105mm gun systems.

Less than two months ago, the future of the Stryker was uncertain, with former House speaker Newt Gingrich (R-Ga.) advising Rumsfeld that the vehicle was not transportable aboard C-130s, a key requirement, and should be scrapped. But now, the decision to fund a fourth Stryker brigade ensures that more than 1,200 Strykers will be produced.

"It's extremely positive news," said Kendell Pease, a spokesman for General Dynamics Corp., the Stryker's manufacturer.

Defense Secretary Donald H. Rumsfeld announced plans yesterday to fund a fourth of six new Army combat brigades.