AT&T Corp.'s pledge to eventually allow competitors to use its cable lines to provide high-speed connections to the Internet drew cool reactions from America Online Inc. and other rivals yesterday, as some continued to insist that federal rules are needed to ensure no company can monopolize access to the global computer network.

"This sounds like a positive step," said George Vradenburg, AOL's senior vice president for global and strategic policy. AOL, the largest Internet service provider, has led the drive to force AT&T to share its network with competitors.

"AT&T is moving toward a commitment for open access," Vradenburg said, adding that "the rubber's going to hit the road and really test this in reality when we try to enter into enforceable agreements."

Even MindSpring Enterprises Inc., which will today publicly announce concurrence with AT&T on the principles that should govern open access, has reservations about the degree to which the agreement closes the debate, an industry source said.

AT&T and MindSpring are expected to sign a letter to be sent today to Federal Communications Chairman William E. Kennard highlighting the agreement. MindSpring, which is the nation's second-largest Internet provider, also is expected to deliver a separate letter to Kennard in which the company will cast the agreement as no substitute for a coherent federal policy, the source said.

AT&T has been embroiled in a national debate over the control of access to the next generation of the Internet ever since it bought Tele-Communications Inc., the nation's largest collection of cable systems. AT&T plans to turn cable wires into conduits for high-speed computer links and telephone service.

AT&T said it would honor a contract that gives Internet service provider Excite At Home the exclusive right to provide Tele-Communications' customers with high-speed Internet access through 2002. Excite At Home manages AT&T's data network and oversees a popular Internet page with links to other World Wide Web sites.

The FCC has declined to regulate Internet access over cable lines. Kennard said he is concerned that doing so would eliminate the cable industry's incentive to upgrade its lines for the new services. MindSpring is expected to urge the FCC to rethink that position and impose rules that would force AT&T to share its cable lines sooner than 2002, when AT&T said the new policy would take effect, the source said.

At a meeting today with Wall Street analysts in New York, AT&T is expected to formally announce a new policy: After the Excite At Home contract expires, AT&T will allow its customers to link directly to an Internet provider of their choice.

An industry source said the agreement with MindSpring did not gain wider endorsement because other Internet providers fear it does not reflect AT&T's real intentions. Some providers worry that the agreement amounts to a political head fake designed to dissuade the FCC from legally mandating the new policy while helping AT&T gain merger approval for its latest cable purchase, Media One Group Inc., the source said.