(Updates with comment from union in second paragraph.)

Dec. 30 (Bloomberg) -- Rio Tinto Group said workers at its Alma smelter in Quebec rejected the company’s final offer for a new labor accord.

The existing labor contract expires midnight tomorrow, Bryan Tucker, a spokesman for Rio, said today by phone.

A government-appointed mediator has scheduled a meeting with both sides at 3 p.m. today, Marc Maltais, a spokesman for the union, said in a telephone interview.

Rio intends to attend the meeting, Tucker said in an e-mail.

The Alma smelter produces just over 400,000 tons a year of aluminum.

--With assistance from Stefanie Batcho-Lino in Toronto. Editors: Charles Siler, Jasmina Kelemen

To contact the reporter on this story: Liezel Hill in Toronto at lhill30@bloomberg.net

To contact the editor responsible for this story: Simon Casey at scasey4@bloomberg.net