MISSISSAUGA, Ont. -- The Canadian Union of Public Employees says it has rejected a contract offer for 435 front-line, administrative and support workers at the Children's Aid Society of the Region of Peel.

The two sides met for nearly 12 hours Wednesday with the help of a provincially-appointed mediator.

CUPE Local 4919 president Sonia Yung said in a statement that a "final offer" from Peel CAS does not meet the needs of the workers.

Yung said progress had been made in resolving a number of issues but the bargaining committee was "surprised and disappointed" when Peel CAS presented its final offer. She did not say what the offer contained.

Yung said the bargaining committee will update members later this week prior to an upcoming lockout or strike deadline, which has been set for 12:01 a.m. Saturday, Sept. 17.

In a statement issued earlier Wednesday, Rav Bains, the CEO of the Peel agency, said they hoped to reach a negotiated agreement "that reflects the nature of the work done by our unionized staff and recognizes the reality of limited funding."

He said the agency must have a balanced budget by law and ensure operational costs do not increase to the point where its services are compromised.

Peel CAS serves the cities of Brampton and Mississauga and the town of Caledon.