The State Department wants to use about two-thirds of its proposed military equipment aid for Pakistan's anti-terrorism programs to help the key U.S. ally upgrade its aging fleet of U.S.-made F-16 fighter planes.

The planes traditionally have not been used in anti-terrorism operations, and Pakistan sees the planes as a chit in its arms race against rival India. Congress must approve the switch, which was requested days before Pakistan's new prime minister, Yousuf Raza Gilani, is due to meet President George W. Bush at the White House.

The Bush administration is feeling its way in its dealings with Pakistan's new leaders, who are friendly to the U.S. but far less closely allied than the formerly supreme leader, President Pervez Musharraf. Musharraf retains his post but with less authority. The prime minister's government has struck proposed partnerships with tribal leaders in the volatile terror-breeding ground along the Afghan border that make U.S. officials nervous.

The request to Congress late last week would allow the key U.S. ally to purchase equipment to upgrade existing planes so that they have similar capabilities to equipment the Bush administration is already selling to Pakistan. The $226 million would come from an allotment already approved for other Pakistan anti-terror operations.

The previous request would have upgraded P3-C aircraft, which often are used in surveillance operations, and modernize AH-IF Cobra helicopters. The helicopter work still would be done using different funding, a State Department official said. The official spoke on condition of anonymity because discussions with Congress are still preliminary.

Switching the money to fix up F-16s would represent a change in the purpose for more than two-thirds of the $300 million that Pakistan will receive this year in U.S. military underwriting for Pakistan's equipment and training. Congress has required that the training and equipment money be spent for law enforcement or to fight terrorism.

F-16s are something of a badge of honor for Pakistan, and a sore point in the history of the U.S. relations with the Muslim nation.

The Bush administration approved the sale of 18 new jets last year. The package included an option for Pakistan to order more jets and to get used aircraft refurbished.

Pakistan signed a deal with Washington to buy the F-16s in the late 1980s, but the agreement was scrapped in the 1990s when the U.S. government imposed sanctions on Islamabad over its nuclear weapons program.

Although Washington lifted the sanctions because of Islamabad's support for the U.S. war on terror, the sale of the F-16s had remained on hold and some lawmakers have continued to criticize the deal, arguing the planes are more likely to be used in a war with India than against terrorists.

U.S. assistance and other payments to Pakistan have totaled $9.6 billion in the six budget years since the Sept. 11, 2001, attacks on the United States, according to the State Department.

The largest payout each year is for what the Bush administration calls "reimbursements" for Pakistan's help in fighting terrorism. Under that program, Pakistan submits claims — such as its costs for providing observations posts along the Afghan border or its costs for taking part in joint operations with the U.S. against Al Qaeda.

The reimbursements amount to some $80 million a month or nearly $1 billion a year.

On top of those payments, the U.S. also gives Pakistan direct aid for humanitarian programs, economic development, military needs and so on — well over $700 million in each of the last two years.