California Gov. Gavin Newsom sent an unusual letter on Saturday to the top judges of the state's four federal court districts. He warned that the Justice Department may ask them for search warrants to seize ballots, voting records or election equipment before California certifies its results.

The letter went to the chief judges of the Northern, Eastern, Central and Southern districts of California. Newsom said he was not aware of any warrant request that had actually been filed. He wrote that he wanted the judges to be prepared in case one arrives.

Along with the letter he included a guide put together by an election law center at UC Berkeley. It walks through the legal limits on federal searches of state election materials. California must certify its results by Dec. 11.

Rising tension with Washington

The warning is the latest step in a weeks-long clash between California and federal officials over ballots the government says may have been sent to noncitizens. State Attorney General Rob Bonta put out an advisory to county election offices on Wednesday about how to respond to federal demands.

On Saturday acting Deputy Attorney General Trent McCotter said he expected the dispute over California's ballots to reach the Supreme Court before Election Day. That would put the nation's highest court in the middle of a state's vote count just as polls close.

So far the courts have sided with California. On Friday a federal appeals panel voted 2-1 against forcing the state to set aside more than 20,000 ballots flagged by the government. Judges found there was no safe way to pull those ballots out once they had been processed.

What county officials are facing

Local clerks have been caught in the middle. Federal prosecutors have sent grand jury subpoenas to some election workers. A judge in San Francisco on Friday barred federal agencies from threatening election staff with charges while the case moves forward.

Newsom has said the state will protect every lawful vote. Federal officials say they are enforcing the law against noncitizen voting, which is already a crime in federal elections.

Election Day is Tuesday, Nov. 3.