WASHINGTON (AP) _ A federal appeals court has upheld a decision by federal regulators to block US West and Ameritech from selling the long-distance service of Qwest Communications Corp. to local phone customers.

The partnerships were blocked last September by the Federal Communications Commission, which said the alliances were illegal.

US West Communications Inc. and Ameritech Corp., had briefly marketed Qwest's long-distance service until they were ordered to stop last year. Under pacts between the companies, Qwest paid US West and Ameritech an undisclosed recruiting fee for each client in the Baby Bells' local phone regions that chooses Qwest for long-distance service.

AT&T, MCI and other carriers argued that the alliances violated a 1996 telecommunications law that forbids Bell companies from providing long-distance service to their own customers. The FCC agreed, ultimately ruling that the Qwest deals were anti-competitive.

In an opinion released Tuesday by the U.S. Court of Appeals for the District of Columbia, a three-judge panel concluded that the FCC had acted reasonably.

``If the (Bell operating companies) could secure this advantage without opening their local service markets, the blunting of the intended incentive would be considerable _ or so the Commission could reasonably find,'' wrote Judge Stephen Williams in the group's opinion.

To provide long-distance service to local customers, a Bell company must open its markets to competitors and get FCC approval. No Bell has done so.