SAN FRANCISCO — Time is up for Volkswagen to meet a federal judge’s deadline to detail how it will make nearly 600,000 diesel cars rigged to cheat on emissions tests comply with clean air laws.

Senior U.S. District Judge Charles Breyer said he wanted to know the timing of the fix and any planned payments to vehicle owners by a court hearing set for today. That is when a deal is expected to be announced between Volkswagen, the U.S. government and private lawyers for the automaker to buy back some of the vehicles and spend just over $1 billion to compensate owners, a person briefed on the matter said.

The agreement would give some owners the choice of having Volkswagen repair their cars or buy them back, but it does not include plans on how to repair the vehicles. Those plans, and the cost of the fixes, apparently are still under negotiation.

Compensation for car owners was among the details Breyer was seeking, but the judge was more focused on ending the ongoing pollution by getting the vehicles to comply with clean air laws.

He said last month that issue at the very least “must be resolved” and threatened a trial this summer if Volkswagen didn’t meet his deadline.

The “deal in principle” includes a maximum amount of spending, but the final details, such as how much each owner would get, are still being worked out. With $1 billion to spend, it works out to about $1,700 per car. But some owners of newer models who get just a software fix may receive little. About 325,000 owners of older cars that require more extensive repairs likely will get more.