National Basketball Association players have set a strike date of April 2 if a contract agreement isn't reached by then, but Commissioner Larry O'Brien said today the threat of a strike was a surprise to him and added, "The NBA intends, and stands ready, to continue good faith negotiations."

The players, frustrated at the lack of progress in negotiations that have gone on for eight months--the old contract expired June 1, 1982--had not spoken of a strike before Monday. But Greg Ballard, the Washington Bullets' player representative, said player representatives voted unanimously at a meeting that day to set the strike deadline.

"Nobody wants to strike," said Ballard, "but if we let this thing keep on going, no one will get anywhere. We felt we had to do something to get things moving."

Ballard said team owners want to reduce their contributions to pension and medical plans, but said the players aren't going to give up gains made in previous negotiations. He said the players also are interested in obtaining a share of cable television monies.

The major stumbling block seems to be implementation of a revenue sharing plan, first introduced by the league in October. That plan would limit salaries in return for guaranteeing the players a fixed percentage of league revenues. Fifty percent is the figure that has been discussed.

The plan would involve the creation of a fund in addition to individual salaries, with the fund disbursed according to a formula developed by the players' association.

An NBA spokesman said that under the revenue sharing plan, all other negotiating points would be moot, because the league would just give the players the money, hypothetically 50 percent of everything--cable television, program sales, etc--and let them do with it as they pleased.

In a prepared statement, O'Brien said the sides had agreed to the plan, but the owners want it started immediately and Larry Fleisher, general counsel for the players' association, doesn't want it to start until 1986.

Ballard said April 2 was selected as a strike date because that gives both sides time enough to work out an agreement and because it comes before the regular season ends, thus involving all 23 teams and not just those in the playoffs.

The next negotiating session is to be held as soon as logistics can be worked out, the league spokesman said.