WEST PALM BEACH, Fla. - Tennis stars Venus and Serena Williams reneged on a deal to play in a 2001 "Battle of the Sexes" match, costing the promoters millions of dollars, an attorney claimed Friday during opening statements in a breach-of-contract lawsuit against the sisters and their father.

"This case is about the sanctity of a contract, a case about men and women giving their word," said John Romano, attorney for promoters Carol Clarke and Keith Rhodes, who are suing the sisters and their father, Richard Williams, for alleged breach of contract.

Clarke and Rhodes, owners of a company called CCKR, allege that Richard Williams committed his daughters to play in the match and that they reneged on the deal. The promoters had not yet secured agreements from any men's stars, Romano said. The promoters are seeking unspecified damages.

The Williams sisters claim their father could not make such a commitment because he did not have the authority to enter into the deal.

"Not one time, not one document will you see where Venus Williams signed any agreement, signed any note, signed any letter, obligating her to participate in a battle of the sexes," the sisters' attorney, F. Malcolm Cunningham, told jurors.

"Similarly, Serena Williams did not sign anything," Cunningham added. "The case begins and ends there."

A first trial in the case ended in a mistrial in December after more than two weeks of testimony. This second trial, before Palm Beach County Circuit Judge Jeffrey A. Winicoff, is expected to last five weeks.

The sisters were present in the courtroom Friday, sitting at a table with two silver laptop computers in front of them. Their father also was present.