Detroit ? Negotiators with the United Auto Workers union and Chrysler LLC have made progress on efforts to reach a new four-year labor contract, but a person briefed on the talks said Sunday that much work remains.

“There are a bunch of committees” that have to reach agreement before a deal can be signed, said the person, who requested anonymity because the talks are private.

Negotiators bargained Saturday and returned to the table Sunday, Chrysler spokeswoman Michele Tinson said, adding that the two sides were making progress.

“We remain optimistic,” she said. UAW spokesman Roger Kerson declined to comment on the talks.

General Motors Corp. already has reached a tentative agreement with the UAW that GM workers are now voting on. The union has not formally picked the second company it will negotiate with, but talks with Chrysler have intensified in recent days.