Sutter Health and Blue Shield of California did not respond to a contract extension offer by the Tuesday deadline, throwing the health plans of 280,000 customers into uncertainty.

Blue Shield executives said they were still reviewing the offer from the hospital group, according to a SFGate.com report. Sutter Health includes the Alta Bates Summit Medical Center in Oakland and Berkeley and the California Pacific Medical Center in San Francisco.

The two sides have been locked in volatile contract dispute over terms and reimbursement rates, and their contract expired Dec. 31.

Dr. Stephen Lockhart, Sutter Health’s chief medical officer, said in a statement that the group was proposing a transition agreement to ensure that patients would “have continued access in 2015 to the doctors Blue Shield promised them during open enrollment.”

Blue Shield provided no response by the noon Tuesday deadline, according to the report. A spokesman for the healthcare group said that they rejected Sutter Health’s statement, arguing that the details are much more complex than what was included in the press release.

The spokesman indicated that the company was hopeful that it could negotiate a contract, but only “under fair and reasonable terms.”

If the two sides are unable to come to an agreement, which would extend the contract through 2015, it would create chaos for 280,000 Northern and Central California customers, who would have to find new doctors and hospitals that fit their plan.

Sutter Health is a not-for-profit health system situated in Northern California and headquartered in Sacramento. It provides health care services to more than 100 Northern California locations.

Blue Shield of California is a not-for-profit health plan provider that was founded in 1939 and is situated in San Francisco it serves 3.4 million health plan members and 65,000 physicians statewide, and was founded by the California Medical Association.