By Michael Martinez and Brian Todd, May 23, 2014, CNN

Los Angeles (CNN) -- The NBA 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.

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 because 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.

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