SOFIA, Bulgaria -- Bulgaria said on Wednesday that it might end talks with Unified Energy Systems on the proposed sale of a thermal power plant for 578.8 million euros ($688 million) unless they resolved outstanding issues this week.

Bulgaria's privatization agency and UES signed a draft contract in October for the long-delayed sale, but obstacles ranging from regulatory to environmental issues have prevented them from closing the deal.

"The option of canceling the deal looks more and more likely. ... I think we can wait until the end of this week at the most," Bulgarian Economy and Energy Minister Rumen Ovcharov said at a news conference. "Apparently Bulgaria has no more time to waste. Either we will sign a deal with UES, or we will have to decide to start talks with the second best bidder or launch a new procedure."

The deal has dragged on since April when UES won a tender to buy the 1,260-megawatt plant in Varna and a smaller one in the Danube river city of Rousse, but anti-monopoly authorities ruled it could buy only one of the two, and UES chose the Varna plant.

Czech firm CEZ placed the second best offer for the plant, followed by Italy's Enel and Greece's Public Power Corp. for the coal-fired plant.

 UES said Wednesday that its net profits to international accounting standards fell 26 percent to 16.4 billion rubles ($572.2 million) in the first half of 2005.