The Federal Communications Commission was ready to vote Thursday to levy the first fine for violation of its new decency standards on a Missouri television station that aired a sexy movie during prime time, FCC sources said.

Commissioners were likely to impose the maximum $2,000 fine against KZKC-TV for its May 1987 broadcast of "Private Lessons," which included scenes of a bare-breasted woman seducing a teenager, said the sources, who spoke on the condition they not be identified.The Kansas City station aired the movie at 8 p.m., a time the FCC has determined children are likely to be in the audience. The FCC's guidelines allow "indecent" material to be aired after midnight to lessen the risk that such programs could be viewed by children.

FCC Chairman Dennis R. Patrick declined to comment Wednesday on the case before the commission voted, but he said that the FCC's record on indecency has been clear.

"While respecting the First Amendment rights of all citizens, we have taken clear and decisive action to enforce the statutory ban on broadcast obscenity and to further restrict the broadcast of indecent material so as to put parents in a better position to control their children's access to this type of material," he said.

Media Central Inc., which owns KZKC, has said the film had been cut by an inexperienced editor and violated company standards, but a fine would be inappropriate because the FCC's indecency guidelines are ambiguous and are being applied to TV for the first time.

The movie, the owners said, was aired little more than a month after the new standards were adopted. The FCC guidelines are being challenged in court by broadcasting groups, news organizations and public interest advocates as being unconstitutionally vague and overbroad.

Media Central acknowledged that the airing of the 1980 sex comedy violated KZKC's "broadcast standards and sense of good taste," but the company said station officials took immediate corrective action after the broadcast, including a clarification of the station's policy on frontal nudity.

Attorney Thomas Davidson, representing Media Central, said it would be premature to comment before the commission acted.

Media Central, based in Chattanooga, Tenn., is awaiting court action on a reorganization plan it filed under Chapter 11 of the Federal Bankruptcy Act.

"Private Lessons" is about a wealthy 15-year-old boy who is seduced by his housekeeper. The film includes several scenes in which the housekeeper is shown bare-breasted.