WASHINGTON — A government lawyer urged a federal judge Thursday not to impose a severe sanction on the Secret Service, despite the agency's repeated delays in producing evidence in a lawsuit alleging racial discrimination.

In a case that has gained national attention, Magistrate Judge Deborah A. Robinson of the U.S. District Court must now decide whether the Secret Service should be forbidden to mount a defense when the long-standing case finally goes to trial.

Robinson has already sanctioned the agency three times for missing deadlines and failing to comply with her orders to provide documents for the lawsuit, brought by 10 African-American Secret Service agents and former agents who charge they were subjected to a culture of racism and passed over for promotions. Many of the allegations of discrimination center on the service's Atlanta office.

In pre-trial testimony, agents have admitted that some relevant evidence in the case had been put into a burn bag and destroyed. And two years after the discovery phase began, the government only recently produced 10 racist e-mails, including one with a joke about lynching, which circulated among senior officials.

The Secret Service has denied that such abuses are signs of overall racial discrimination at the agency.

In a sign of the contentious struggle, lawyers for the service this week filed documents citing offensive e-mails circulated or received by the chief plaintiff in the case, Reginald G. (Ray) Moore, an Atlanta native and current Secret Service agent who filed the lawsuit eight years ago.

Moore's e-mails included photos showing African-American women in unflattering, partially clothed poses and jokes about black wives and mothers being prone to violence.

Moore, who attended the hearing Thursday, declined to discuss the e-mails and referred questions to his lawyers.

Desmond E. Hogan, an attorney for the plaintiffs, said that there are "obvious reasons" that the Secret Service would use the e-mails to embarrass Moore.

"I think that the e-mails were unfortunate, and I'm sure Ray feels bad about them," Hogan said. He added that the plaintiffs have evidence of an "ocean" of racism, including e-mails from supervisors referring to the Ku Klux Klan and frequent use of the "N" word.

The Secret Service, which protects the president and other top officials and investigates counterfeiting of U.S. currency, says that its agency has "zero tolerance" for racial bias.

In a statement, the service said African-Americans make up 16 percent of its employees and 15 percent of supervisors and asserted that African-American special agents tend to be promoted faster than their colleagues.

Lawyers for the plaintiffs said those assertions are contradicted by an expert who has analyzed the Secret Service statistics.

A trial is expected in the case sometime next year.