The Serbian government said on Friday it had extended a tender to sell the country's largest crude steel plant, Zelezara Smederevo, to June 11 at the "requests of participants."

The list of bidders for the plant include Luxembourg-registered United Pilsen S.A. owned by Russian businessman Igor Shamis, Ukraine's Donetskstal steel maker and Russia's Ural Mining and Metallurgical Company. The government did not say which bidder requested the extension.

The plant, 70 kilometers from Belgrade, was previously owned by the U.S. Steel corporation and was on the brink of bankruptcy.

U.S. Steel bought the plant in 2003 for $33 million and invested 300 million euros in it, but the plant failed to reach a designed annual output of 2.2 million tons. The plant's losses were about 100 million euros in 2011.

The Serbian government purchased the plant from U.S. Steel in January 2012 for a symbolic price of $1 to prevent closure of the enterprise, which employs more than 5,000 people. It then sought a strategic investor for the plant.