By Ben Dummett 

TORONTO--Canada's Cameco Corp. late Friday said production remains suspended at its flagship uranium mine in Saskatchewan and a lockout of the mine's unionized employees is still in effect because of an ongoing impasse over contract negotiations.

The McArthur River mine and its Key Lake mill operation in northern Saskatchewan is the world's largest uranium mine and accounts for about 10% of the world's annual uranium supply. Cameco, based in Saskatoon, Saskatchewan, owns 70% of McArthur River, and Areva S.A. owns the other 30%. The two also share ownership of the Key Lake mill operation.

In a Friday statement, Cameco indicated it has sufficient inventory of uranium to meet customer orders for this year despite the disruption. "The work stoppage is not expected to affect the company's 2014 uranium delivery commitments to customers," Cameco said.

A Cameco spokesman said it was too early to say how long production at the mine could be halted. "We believe we [tabled] a competitive and fair offer," the spokesman said, while declining to provide specifics.

A representative for the United Steelworkers Local 8914, the union representing the 535 locked out workers, couldn't immediately be reached. Some analysts have forecast Cameco has uranium inventories representing about six months' worth of sales.

Earlier this week, Cameco had issued a 72-hour lockout notice covering the McArthur River mine and Key Lake mill after the union issued a strike notice that was to take effect Saturday.

On Friday, Cameco said it presented its final contract offer to the union's bargaining committee on Thursday, but the offer was rejected. The company didn't disclose details of the offer.

The unionized workers have been without a collective agreement since the end of 2013. Contract talks started in November.

Write to Ben Dummett at ben.dummett@wsj.com

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