The National Basketball Association and the players union negotiated for only 20 minutes in New York yesterday before the players walked out of the meeting. Afterward, Larry Fleisher, general counsel for the union, said he would be "shocked" if the players do not strike.

After the two sides met for a total of 12 hours Monday and Tuesday, there was speculation that the owners and players were close to a compromise that would avert a scheduled April 2 strike. But yesterday's development was described as "a serious setback" by one of the owners.

The sides have apparently agreed on a compensation plan that would put a ceiling on a team's total payroll and guarantee players a fixed percentage of the league's gross revenues. The problem has arisen over what percentage to pay the players and when to implement the plan.

A spokesman for the NBA said that at yesterday's negotiating session, the players association rejected the owners' offer of 50 percent of the gross revenues for the next four years. The spokesman said the players demanded 53 percent, then broke off discussions and left the meeting.

The owners originally offered 40 percent, but Fleisher said last month the players "would take no less than 55 percent in the new agreement."

Fleisher said then the owners paid approximately 57 percent of their gross to the players last year. The league lost about $16 million last year.

One owner estimated a strike would cost the owners $20 million to $30 million.

"It is clear to us that, based on today, we've been wasting our time," Fleisher said yesterday. "My feeling is there is no alternative. There will be a strike April 2."

The strike deadline is two weeks before the end of the regular season. The players picked that date so a strike would involve all 23 teams and not only those making it to the playoffs, and would have the greatest financial impact on the owners.

Most of the $22 million the NBA gets from CBS for network television rights is to be paid during the playoffs, when most games are scheduled to be televised.