Story highlights Clippers decline to comment on NBA announcement

NBA will proceed with hearing on forced sale on June 3

Shelly Sterling is negotiating with NBA about voluntary sale, source says

Donald and Shelly Sterling agree to sell Clippers voluntarily, source says

The National Basketball Association will proceed with a vote to force a sale of the Los Angeles Clippers, rebuffing an effort by co-owners Donald and Shelly Sterling to sell the franchise voluntarily, NBA spokesman Mike Bass said Friday.

"We continue to follow the process set forth in the NBA Constitution regarding termination of the current ownership interests in the Los Angeles Clippers and are proceeding toward a hearing on this matter on June 3," Bass said.

His announcement followed reports earlier Friday about how Donald and Shelly Sterling agreed to a voluntary sale of the NBA franchise as the league prepares a vote on a forced sale, according to a source familiar with the situation.

The couple have an agreement to allow Shelly Sterling to do the negotiations, and there have already been discussions between her and the NBA, according to the source.

Attorneys for the Sterlings, who earlier declined to comment about the couple's effort for a voluntary sale, weren't immediately available to react to Bass' statement. The Clippers declined to comment on the NBA statements, spokesman Seth Burton said.

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Friday's events signal how the NBA is standing by its ultimatum that a vote will be held on a forcible sale.

For their part, the Sterlings appear to be running out of options -- short of suing the league -- and analysts say such a lawsuit wouldn't be inconceivable, as Sterling is an attorney well versed in litigation.

Meanwhile, pressure grows for Donald Sterling, a real estate billionaire. He faces a deadline Tuesday to respond to the NBA's proposal to terminate his ownership in the team because of racist remarks he made.

The NBA has banned Donald Sterling for life , and the league is advancing a vote by other team owners that would force the couple to sell the franchise.

The ban and pending vote -- along with a $2.5 million fine against Donald Sterling -- arise from how he slurred African-Americans.

A voluntary sale would be a new maneuver for the Sterlings. Last week, Donald Sterling hired an antitrust lawyer to fight the NBA about the proposed forced sale. And his wife has said she wanted to keep an ownership stake in the team but doesn't want to be the controlling partner.

The couple own the team through a trust. They are also estranged, Shelly Sterling's attorney has said.

The NBA contends it was damaged by the 80-year-old's racist remarks to associate V. Stiviano, 31, that were captured on an audiotape and posted online in April by TMZ and in an interview with CNN's "Anderson Cooper 360° ."

"Among other things, Mr. Sterling disparaged African-Americans and 'minorities'; directed a female acquaintance not to associate publicly with African-Americans or to bring African-Americans to Clippers games; and criticized African-Americans for not supporting their communities," the NBA said in a recent statement.

In order to terminate the Sterlings' franchise rights, three-fourths of the team owners (23 of 30) would have to vote to sustain the charge and force a sale. Because Sterling is banned from any NBA activities, he is not allowed to vote, but the Clippers will have a vote, the NBA said.