WASHINGTON (AP) _ The Federal Communications Commission moved Thursday toward a possible crackdown on children's TV programs based on toys, but an official said the agency was ''twisting and turning'' to steer clear of shows such as ''Sesame Street.''

Critics contend that programs such as ''He-Man'' and ''G.I. Joe'' are thinly disguised sales pitches and have urged the FCC to declare such shows to be 30-minute commercials.

The commission, however, wasn't willing to go that far.

''The mere fact that a story line ... is built around a toy being sold on the market would not make it a program-length commercial,'' said Regina Harrison, a lawyer in the FCC's mass media bureau.

The commission, she said, was ''twisting and turning trying to reach a definition that won't cut out shows'' such as ''Sesame Street.''

The commission, under orders from Congress to complete a 3-year-old investigation into so-called program-length commercials, proposed defining such programs as any children's show ''associated with a product in which commercials for that product are aired.''

Previously, the commission defined program-length commercials as material ''so interwoven with, and in essence auxiliary to, the sponsor's advertising'' that the entire program is in effect a commercial.

Peggy Charren, president of the Action for Children's Television, said manufacturers don't advertise their toys on shows based on their products for fear children won't notice the ads.

She said the FCC's proposed definition would not solve the problem of shows being used to promote toys.

The commission invited public comment on what penalties, if any, should be imposed on program-length commercials. Harrison said violators could receive fines or have their licenses threatened at renewal, or both.

The commission also said it would consider during license renewal whether a station had provided programs specifically designed to meet the educational and informational needs of children.

The commission, in the same 5-0 vote Thursday, proposed implementing ad time limits that Congress ordered as part of the Children's Television Act of 1990.

Those limits are 10.5 minutes per hour on weekends and 12 minutes per hour on weekdays on children's shows, including cable TV.

The rules are to take effect in April, and violations could lead to fines from $25,000 to $250,000.

The commission lifted similar restrictions in 1984, but congressional testimony showed that advertising on some programs increased to 14 minutes per hour. A federal appeals court in 1987 ordered the FCC to reconsider its decision.