WASHINGTON (AP) _ A price break on federal licenses for three communications companies won approval as part of a new world trade accord but senators are vowing to reopen the matter next year.

The provision, which reduces what the companies will pay for licenses to provide the next generation of mobile phone service, is part of legislation ratifying the expansion of the General Agreement on Tariffs and Trade.

The Senate approved it, 76-24, on Thursday even though the licensing provision was much criticized.

''At the last minute, the administration and the companies cut a back room deal. ... And who pays? The American taxpayer gets the short end,'' complained Sen. Howard Metzenbaum, D-Ohio, a GATT opponent.

But, in the end, the provision stayed in because under the special fast- track rules for considering trade bills, no amendments were in order. The Senate's choice was either to reject the 124-nation pact in its entirety or accept the license discounts.

''We can't ... say, 'Hey, let's do it all over again. We don't like one provision.' That's not possible,'' said Sen. Don Nickles, R-Okla., who supported GATT but opposed the license discounts.

The provision was in the GATT bill as part of the $12 billion package to offset lost tariff revenues during the accord's first five years. Though reduced from what other companies will pay, the licenses for the three companies in question are counted as a revenue-raiser because the companies originally were supposed to get them for free as ''pioneers'' of new technology.

The three companies are: American Personal Communications, an affiliate of The Washington Post Co.; Cox Enterprises Inc., an Atlanta-based media company whose holdings include The Atlanta Constitution; and Omnipoint Corp., a small privately held company in Colorado.

The three will be the first to receive the new licenses from the Federal Communications Commission at auctions starting Dec. 5. Exactly how much they will pay is unclear because the formula in the trade pact is based on what other companies end up paying.

Sen. Bob Packwood, R-Ore., defended the discounts, brokered by House Energy and Commerce Committee Chairman John Dingell, D-Mich., as both fair and necessary to head off a lawsuit.

''Was this a sellout to the Washington Post? No. ... It was a settlement ... avoiding the risk of getting no money and having to give these three licenses away,'' Packwood said.

As part of the understanding to secure Senate Republican Leader Bob Dole's support for GATT, the Clinton administration agreed to review the results of the telephone license auctions.

White House Chief of Staff Leon Panetta wrote Dole that if the government's return isn't big enough, the administration will seek legislation that would ''adequately compensate the United States.''

''We're going to review it next year,'' Dole said just before the vote.