Anthem Blue Cross and Blue Shield and Hartford HealthCare sought to assure the insurer's customers Friday that they are continuing negotiations toward a new contract and are committed to reaching a new agreement before the Sept. 30 expiration date.

Anthem this week sent letters to its customers notifying them that, unless an agreement is reached, customers' care at Hartford HealthCare facilities would be out-of-network for reimbursement purposes as of Oct. 31, meaning patients would face higher costs or have to seek care elsewhere. The William W. Backus Hospital in Norwich is part of the Hartford HealthCare system. Similar letters were sent to customers in August. Sarah Yeager, spokeswoman for Anthem, said the state Department of Insurance requires insurers to notify customers at least 30 days before a potential termination of coverage benefits.

Anthem and Hartford HealthCare said Friday they are "working diligently ... to reach a fair resolution."