San Bruno B.A.R.T.

  San Francisco Mayor Willie Brown suffered a rare veto override Tuesday, when city supervisors voted overwhelmingly to set aside airport money for a lawsuit against a contractor accused of cheating the airport out of tens of millions of dollars.

  The Board of Supervisors voted 10-1 to appropriate $2.5 million from the airport's surplus to pay for the first year of litigation against Tutor-Saliba Corp., which denies any wrongdoing on its part in building about $1 billion worth of San Francisco International Airport's latest expansion.

  In so doing, the supervisors declined to take up an alternative, last- minute Brown proposal that would have had the airport lend $7.5 million, with interest, for the suit, with the general fund on the hook for the money if Tutor-Saliba were to win.

  Now the matter will go to the Brown-appointed Airport Commission, which has so far refused to pay for City Attorney Dennis Herrera's suit, because commissioners say Herrera's evidence against Tutor-Saliba, particularly of commercial fraud, is not convincing.

  Herrera accuses Tutor-Saliba of overbilling and using fake minority subcontractors to qualify for city bids.

  The Airport Commission is not compelled by city law to spend money on Herrera's suit.

  However, Supervisor Aaron Peskin, Herrera's champion on the board, is chairman of the finance committee that considers numerous airport funding matters, and he has said there could be consequences if the airport refuses to do so.

  "I'm going to be hard pressed to approve new capital expenditures at San Francisco International Airport if airport staff and the airport commission are unwilling to go after fraud," Peskin said.

  Tutor-Saliba owner Ron Tutor called the supervisors' vote ''terribly unfortunate."

  "No one ever questions the quality of our work," Tutor said. "I'll stack my personal integrity against theirs (Herrera's staff) any day."

  The mayor, who also questions the strength of Herrera's case, said in his veto message that his alternative funding proposal was meant to get Herrera the money that he so badly wants.

  After Tuesday's vote, Brown spokesman P.J. Johnston said the mayor "offered an olive branch, and it was soundly rejected by this board."

  "He (Brown) put forward a way to unify San Francisco's political leadership behind this lawsuit," Johnston said. "The Board of Supervisors today clearly seems hell bent on political gridlock."

  Supervisor Tony Hall, the lone supervisor supporting the mayor, said he thought Brown's proposal was good because airport officials would support it and it could bring money to the general fund, which has a deficit that is estimated to be about $347 million.

  Herrera's office, however, told supervisors that Brown's proposal raised numerous issues regarding use of airport funds that would require negotiations with the Federal Aviation Administration and numerous airlines, but work on the lawsuit must begin immediately.

  Supervisors also questioned the wisdom of Brown's alternative funding proposal, particularly the idea that the deficit-wounded general fund -- which pays for law enforcement and social services, among other things -- should assume liability for the lawsuit but only potentially win one-third of any punitive damages.

  "I'm not a sucker. That's a bad deal," said Supervisor Chris Daly.

  "I think this somewhat craven and somewhat obstructionist," said Supervisor Tom Ammiano.

  The airport should pay for the lawsuit because it was the entity that allegedly was cheated, and it is the airport that should get any monetary award, Peskin said.

  Peskin and some other supervisors said they were still willing to study Brown's proposal for possibly retroactive adoption.

  After the veto override, airport director John Martin said he hoped within two weeks to flesh out details of the mayor's idea for further consideration by supervisors.

E-mail Patrick Hoge at phoge@sfchronicle.com.