The Army outlined yesterday a restructuring of its modernization program, the Future Combat System, increasing the cost by between $20 billion and $25 billion, accelerating the deployment of key technology and adding new models of drones and ground vehicles.

The program, which is critical to the Army's transformation into a lighter, more mobile force, was originally expected to cost about $92 billion. Boeing Co. and Science Applications International Corp. are jointly managing the project.

The program aims to connect soldiers to a mobile and wireless network to assist them in battlefield decisions. It would replace the current fleet of ground vehicles with a mix of high-tech manned and unmanned ground and aerial vehicles.

The massive modernization effort has been dogged by questions about its complexity and the pace of progress on the futuristic drones and ground vehicles. The high-tech renovation will require more than 30 million lines of software code. The program "has so many moving pieces and they are so technically challenging it would be almost unbelievable to suggest it could stay on its original schedule," said Loren B. Thompson, defense consultant and chief operating officer of the Lexington Institute, an Arlington think tank.

Army Chief of Staff Gen. Peter J. Schoomaker acknowledged the challenges Wednesday, telling Congress that as originally structured the program had only a 28 percent chance of success. The revisions boost its chances to more than 70 percent, he said.

Under the restructuring, the military will delay deployment of the first fully modernized unit, which will include about 2,500 soldiers, for two years, until 2014. Instead the Army will create an experimental unit in 2008 to begin testing some of the technology, including missiles stored in remote locations that a soldier could deploy through the network.

The cost increase will cover several changes to the program, including adding an armed unmanned robotic vehicle, a recovery and maintenance vehicle, two classes of unmanned aerial vehicles and an intelligent munitions system, also known as a "smart mine," which a soldier could turn on and off remotely or program to deactivate in 30 days.

"This is a very prudent and logical progression" of the program, said Army Lt. Gen. Joseph L. Yakovac Jr., military deputy to the assistant secretary for acquisition.

Some of the changes were prompted by experiences in the Iraq war, Army officials said. The Army will equip all eight manned vehicles in the program with self-protection technology for attacking incoming missiles. The previous plan called for the technology to be applied only to vehicles that would operate at the front. The change is an acknowledgement that the boundaries of the traditional battlefield no longer exist, Army officials said.

Chicago-based Boeing, which serves at the lead manager of the program, said the changes were good news. "Now we have to show the flexibility to get these new capabilities to our soldiers even faster," Dennis Muilenburg, Boeing's vice president and general manager of the project, said in a statement.

The 2005 defense appropriations bill includes $2.9 billion for the program, $1.2 billion more than this year but $268 million less than was requested.