United Steelworkers negotiators are in almost round-the-clock bargaining sessions with ArcelorMittal as the two sides attempt to reach a labor agreement, union officials said Tuesday.

The current agreement for the 14,000 steelworkers at 14 of ArcelorMittal's domestic facilities expires Sept. 1 unless both sides agree to extend its terms until a new labor pact is reached.

"We are working day and night trying to reach an agreement," said USW Local 1010 President Tom Hargrove. "I am very optimistic at this point."

The steelworkers negotiating team resumed negotiations with the company Monday following a 10-day interruption. After the talks recessed Aug. 8, an ArcelorMittal spokeswoman said the two parties had made a lot of progress and "remain committed to the process of concluding an agreement before the Sept. 1 expiration of the current agreement."

The company couldn't be reached for comment Tuesday,

"We are working diligently and fully expect to achieve a contract that is fair and equitable for our members and retirees," said Jim Robinson, USW District 7 director.