Wolf Trap patrons could see slightly higher ticket prices and fewer cultural programs as a result of an agreement in which Congress will forgive about $9 million in interest on a government loan to the Wolf Trap Foundation.

Under the agreement, the foundation, which oversees the Vienna performing arts center, will repay about $8.5 million in principal over 25 years. That will remove an obligation the foundation has had since 1982, when the Filene Center was destroyed by fire.

Congress gave the foundation $17 million to rebuild the center. About $9 million was a grant, and the rest was a loan.

The foundation raised more than $7.2 million during 1982 and 1983 to repay the loan, but instead had to use the money to cover cost overruns in rebuilding the open-air theater where concerts and shows are staged.

The foundation defaulted on the loan two years ago, and its officials had scrambled since then to get some relief from Congress.

Charles A. Walters Jr., senior vice president and chief financial officer of the foundation, said that under the agreement, Wolf Trap will repay about $215,000 in each of the next three years and about $359,000 in each of the following 22 years.

John Camp, a member of the foundation's board of directors, said the loan payments may require the foundation to raise ticket prices "a dollar or two."

"The foundation feels very strongly that we have come to grips with this," said Walters, who said he does not expect major changes in the operation of Wolf Trap, which sits on 100 acres of farmland donated to the government in 1966.

If no agreement with Congress had been reached, the government could have seized the foundation's assets, which officials say include about 30 undeveloped acres.

Wolf Trap has featured a wide variety of performers since it opened in 1971 as the only national park dedicated to the performing arts. Although loan payments would represent a small portion of the foundation's $13 million annual operating budget, Walters said, the payments could result in fewer cultural programs -- such as ballets and operas -- that traditionally cost more to produce than they bring in.

"It makes the foundation's task a little more difficult in being able to subsidize some fine arts programs," Walters said.