NEW YORK (CNN/Money) - American Express has taken measures to protect its cardholders from identity theft, but now the company is facing its own case of brand identity theft, according to a news report published Thursday.

The New York Times reported the credit card giant is facing a lawsuit filed by a California businessman over the "My life. My card." tagline the company has used in an ad campaign featuring celebrities like Robert De Niro, Ellen DeGeneres and Tiger Woods.

Stephen G. Goetz, a credit card marketer in San Francisco, claims American Express (Research) stole his idea for the slogan after he pitched it to the company, according to the newspaper.

In court filings, the financial services company has maintained it owns the legal rights to the slogan, which it says was created by advertising agency Ogilvy, the report said. American Express spokeswoman Judy Tenzer told the Times the company has a policy of not commenting on pending litigation.

Lawsuits over trademark slogans are common and often are dismissed, but a judge ruled earlier this week that the issues in this case can go to trial, possibly as early as December, the newspaper reported.

The case hinges on whether American Express came up with the idea on its own or took it from Goetz, the Times said. Goetz's lawyer, Micah Jacobs, said in the report that American Express had not been forthcoming with materials proving they developed the slogan.

But even if Goetz can prove he came up with the tagline, it may be too general for him to make a strong ownership claim, the report added.

"Unless you have an association beyond its words, you don't have anything," Thomas F. Holt Jr., a lawyer at Kirkpatrick & Lockhart who is not involved in the case, told the newspaper.

American Express spent more than $88.9 million on credit card advertising in the first quarter, the report said, citing TNS Media. Much of that was spent on the "My life. My card." campaign that began in November, it said. American Express said the television commercials created as part of the campaign created an "emotional and practical" connection with consumers, the report added.

The newspaper said both sides in the case have hired legal firms in preparation for the fight, which is potentially worth millions of dollars, but that informal talks have been held as well.

The case could get more complicated now that J.P. Morgan Chase has unveiled its new slogan, "Your Choice. Your Chase." Jacobs told the newspaper.

"It's sort of ridiculous. I'm trying to figure out how that plays in here," the report quoted him as saying.

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