The American Civil Liberties Union (search) plans to sue Los Angeles County if it does not remove a cross from its official seal.
County officials say the cross represents the Spanish missions (search), which are part of California's history.
They add that it would be expensive to redesign the county seal, which was designed in 1957 and appears on most official county property: walls, documents, water bottles, uniforms, cars and trucks.
On Friday, the ACLU gave the county two weeks to eliminate the seal.
"What is the message that it sends?" said Ramona Ripson of the ACLU. "What that message is to everyone in California is one of Christianity, and we are a state of diverse people."
Last month, the threat of litigation by the ACLU forced the city of Redlands, about 50 miles east of Los Angeles, to redesign its 40-year-old logo, which also included a cross.
"Here you have this radical left-wing organization whose own symbol should be the hammer and sickle," said Mike Antonovich (search), one of five Los Angeles County supervisors. "They are using pressure tactics trying to rewrite history."
Some local officials argue that the cross simply reflects history. The ACLU says that shouldn't matter because some members of the public find it offensive.
The county has asked its lawyers for a legal opinion on whether to fight the ACLU.
Click here to watch a report by Fox News Channel's William La Jeunesse.