The Pentagon plans to add about $1 billion next year to the budget for special operations forces, the commandos who are playing a central role in the war on terrorism, a senior defense official said Thursday.

The Pentagon's proposed 2004 budget, which has not yet been submitted to the White House for final decisions, calls for about a 20 percent increase in the special operations forces' budget and an 8 percent increase in numbers of troops, the official said. He provided the information to reporters on condition of anonymity.

Another official, also speaking on condition of anonymity, said that amounted to about a $1 billion increase in the budget and about 4,000 more soldiers. Many of the extra troops would be for the Army's 160th Special Operations Aviation Regiment, whose crews specialize in flying combat troops behind enemy lines.

The decisions by Defense Secretary Donald H. Rumsfeld reflect his publicly stated belief that the Army's Green Berets, the Navy's SEAL commandos and the Air Force's special operations forces should play an even larger role in hunting down and killing terrorists .

The proposed budget increase, from the current $4.9 billion to about $6 billion in the budget year starting next Oct. 1, would pay not only for additional aircraft such as MH-47 helicopters but also for additions to the operational planning staff at U.S. Special Operations Command headquarters, the official said.

The Pentagon plans additional budget increases for special operations forces beyond 2004, although it has provided no details.

With next year's budget gain, the Special Operations Command hopes to acquire 13 additional MH-47 helicopters, one official said. It lost one MH-47 this year in the Philippines and another in Afghanistan. A number of others were badly damaged in combat in Afghanistan. The aircraft is a mainstay of the 160th Special Operations Aviation Regiment.

Another priority for Special Operations Command is the MH-53 Pave Low, an Air Force helicopter. The fleet was to have been phased out in favor of the CV-22 Osprey tilt-rotor aircraft, but the Osprey encountered problems during flight tests and its entry into the force has been pushed back. Thus more money is needed to keep the MH-53 in flying condition longer.

There currently are 47,000 active-duty and reserve special operations forces. In addition to the 160th Special Operations Aviation Regiment, psychological operations units are expected to get many of the new soldiers, one official said.

The increase in personnel is the largest in many years for special operations forces. The forces' numbers stagnated in the 1990s.