The Los Angeles Lakers failed again yesterday in their attempt to be assured of the draft rights to Virginia all-America Ralph Sampson, when San Diego refused to sell its No. 1 choice in the June 29 NBA draft for $6 million and other considerations.

Unless Los Angeles can make a deal for San Diego's pick--which would guarantee the Lakers the right to draft Sampson--sources say the 7-foot-4 center will remain at Virginia for his fourth and final year. A 50-50 chance of playing with the Lakers and Kareem Abdul-Jabbar is not enough to make Sampson leave, the sources say.

Sampson has until midnight Saturday to enter the NBA draft. The coin flip to determine whether Los Angeles or San Diego selects first takes place May 20.

"Los Angeles has made us a wonderful offer and we know that would be a wonderful place for him to play," San Diego General Manager Ted Podleski said yesterday. "But we feel that San Diego is not a bad consolation. We've got something cooking here. We've got a pretty good young team that we'd like to improve.

"If they (Los Angeles) make us an offer that would improve our team substantially, then we would make the deal," Podleski said. "It's a day-by-day, hour-by-hour situation."

Laker General Manager Bill Sharman told the Los Angeles Times he was not optimistic about securing San Diego's pick. "They don't feel what we've offered is good enough," said Sharman. "It doesn't look like we're going to get anything accomplished. All the reports we get are that he's not coming out unless he comes to the Lakers. If that's the case, they (the Clippers) are turning down an awful lot."

Sharman did not reveal the specifics of the Los Angeles offer, but did say it involved "a lot of money, draft picks and other considerations."

San Diego owner Donald T. Sterling said yesterday he was offered the $6 million by Laker owner Jerry Buss at a party in Beverly Hills on Tuesday night. Sterling reportedly said he would accept $10 million plus a player, but Buss balked at including a player.

Sampson, college basketball's player of the year the past two years, has been unavailable this week for comment on his status. A University of Virginia spokesman said yesterday that Sampson will probably make his decision known late today or sometime Saturday.

Sampson turned down approximately $400,000 per year from the Boston Celtics after his freshman year, $800,000 a year from Dallas and Detroit after his sophomore year, and could make $1.5 million this year from Los Angeles or San Diego.

Sampson's bargaining power could be drastically reduced next year if the first team drafting is one of the NBA's poorer franchises and could not afford to offer Sampson $1 million per year.

When asked if San Diego, which had the second-worst record in the league this year, could afford Sampson, Podleski said, "Whomever we draft, we'll sign, no matter what."

Seven underclassmen have already decided to forgo their final year of amateur eligibility to enter the NBA draft: Quintin Dailey of San Francisco, Terry Cummings of De Paul, Dominique Wilkins of Georgia, Cliff Levingston of Wichita State, John Bagley of Boston College, LaSalle Thompson of Texas and Rob Williams of Houston.

North Carolina's James Worthy, who is expected to be the No. 1 choice overall if Sampson remains at Virginia, will probably announce today that he is leaving school for the NBA. Clark Kellogg of Ohio State also is expected to announce in favor of the draft.