MONTREAL - ArcelorMittal Mines Canada chief executive Serge Miller is retiring, 36 years after he began his climb through the ranks of the iron ore company.

Miller, 60, is stepping down on Friday after running the Canadian subsidiary of the world's largest steelmaker for nearly three years.

In that time, he oversaw the company's plans for a $2.1 billion expansion of its iron ore concentrate production in Quebec this year to 24 million tons. He also worked on a corporate reorganization.

Until a successor is chosen, Miller's responsibilities will be assumed by Steve Wood, ArcelorMittal's vice-president of iron ore operations for the Americas region, and the executive committee.

Spokesman Eric Tetrault says someone will likely be named as a permanent head of the Canadian operations, but the company will take the time to first finish its reorganization.

"We're just pursuing our thinking about how the organization should look like in order to meet market needs, so those decisions are for later but they are part of a wider reflection we should have on who should do what," he said in an interview.

Tetrault said Miller's retirement has nothing to do with the recent sale of a 15 per cent stake in its operations to an Asian partnership for $1.1 billion in cash.

"It's a more stable market for iron ore but it's a more demanding market right now so we need to put a lot of efforts to remain competitive," he added.

ArcelorMittal Mines Canada produces about 15 million tonnes of iron ore concentrate and about nine million tonnes of iron oxide pellets annually. It employs more than 2,000 workers at several facilities in Quebec, including Mont-Wright, where the company has one of the largest open-pit mines in North America, as well as an iron ore concentration plant.

Miller, a native of Gaspe, Que., had climbed the corporate ladder at Quebec-Cartier for more than 30 years before it was acquired by ArcelorMittal in 2007. Prior to his appointment in March 2010, he was chief operating officer.

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