The parties still differ on "key issues," such as pension plan changes and "contract language related to seniority rights and employee turnover," the Steelworkers Local 9700 union said in a statement.
The union plans to meet with its members this week to discuss the state of the negotiations and said it will not be communicating with the media during the talks.
In May, a judge ordered ABI to stop using the services of non-union electrical employees and provide the state with a list of any recently hired workers.
ABI locked out more than 1,000 union employees on 11 January and has been operating only one of the facility's three potlines since then. When fully operational, the smelter is able to produce as much as 400,000 t/yr.