American Broadcasting Companies Inc., whose top executives have been sharply critical of regulatory restraints on the television network role in cable television, yesterday announced a joint effort with Warner Amex Cable Communications Inc. to produce and distribute cultural programming to cable subscribers.

Although financial details of the unique arrangement were not disclosed, the venture brings together the programming experience of ABC and the cable television expertise of Warner Amex, which recently has won major cable franchising victories in Cincinnati and Dallas, adding to what was the nation's fifth-largest cable system operator. It is the first formal announcement by a television network of its cable television programming plans. a

"This is probably the tip of the iceberg," Herbert Granath, vice president of ABC Video Enterprises, said in an interview. "It is the first entry by one of the major networks into pure cable programming and probably will harbinger the entry of other major production companies into pure cable programming. That means that specialty programming, which has been the promise of cable, will begin to be realized." Granath said ABC would announce a second programming venture next year.

CBS Inc. also has indicated that it plans to get into the cable television business, disclosing limited details of a plan for extensive cultural programming.

The ABC service, which is expected to be introduced in April, will be called "Alpha" and will be advertiser-underwritten cable service offering 2 1/2 to 3 1/2 hours of performing and visual arts programs.

"We are ready to go, even if we don't get a dime's revenue from advertisers for the first year," Granath said.

Warner-Amex, which is a partnership involving Warner Communications Inc.

and American Express Co., through a subsidiary will provide satellite transmission space that it used for a children's programming network. More than 700 cable system operators reaching about 3.5 million subscribers will have access to the new system. It is estimated the network will have 6 million subscribers by the end of next year.

In addition, Warner Amex also will provide the marketing of the shows to cable operators. The two companies will handle the advertising and promotion. c

ABC said the service will offer arts programming ranging from studies of famous paintings to music, complete ballet works, plays and profiles of the artists.