The board of the county's main transit agency voted Thursday to delay committing any funds to the Gold Line extension until November.
The delay means that the Metropolitan Transportation Authority will miss the deadline to receive $320 million in federal funding for the project.
"November will be too late," said Habib Balian, chief executive officer for the Gold Line Foothill Extension Construction Authority. "We'll have to wait until next year."
The board justified the delay to November to await the results of an expected county ballot measure to increase sales tax by half a cent to fund transit projects.
The group voted to approve preliminary language for the measure on Thursday, and voted on a list of projects to be funded by the measure.