The United States Football League will expand the applications of its instant replay rule and modify its rule on downing ball-carriers, effective immediately.

Instant replay now will be used for challenges of calls when the status of the ball is involved, such as fumbles, pass completions, incompletions or interceptions; penetration of the goal line; whether a kicked ball has been touched by either team; or whether a play is out of bounds.

"We viewed our use of instant replay as an evolutionary process and will expand the list of situations in which an official's call may be challenged," said Commissioner Harry L. Usher.

The first reversal of an officiating call after instant-replay review came in Monday night's 36-17 victory by the Gamblers over the Denver Gold in Houston. A 53-yard pass completion, Jim Kelly to Vince Courville, was called good -- until word was relayed that the camera caught Courville making the catch out of bounds.

Chiefly for the health and welfare of quarterbacks, the league now has eliminated the need for defensive contact on a ball-carrier when he has voluntarily slid to the ground.

The changed rule calls for the whistle "when a voluntarily sliding runner's body hits the surface"; the ball will be spotted at the point of contact with the ground, rather than where the slide ends.

"The NFL has now decided to test instant replay, on the one hand," Usher noted, "and we are recognizing the validity of their recent move to further protect quarterbacks and other ball-carriers. I think that a continuing look at the rules is healthy. It is one of the benefits of competition," he said . . .

Speaking of which, Usher has a date Thursday in New York with the agent for University of Miami quarterback Bernie Kosar.

"We haven't ruled out any of the options available to Bernie, and that includes playing in the USFL," said John Geletka, the Youngstown, Ohio, dentist who is Kosar's agent. "We aren't going to wait until the April 30 (NFL) draft to make a decision on where Bernie will play."

The Orlando Renegades hold his USFL rights.

Kosar, giving up college eligibility, said last week he would like to play for Cleveland of the NFL. The Browns tried to make a deal with the Houston Oilers, who have catbird-seat draft position, but Oilers General Manager Ladd Herzeg says he will not deal with any of the nine NFL teams interested in Kosar if they try to set conditions on a trade. Browns owner Art Modell now says his deal would have to be contingent on Kosar coming to contract terms.