Glencore Xstrata, the global commodity trader and metals producer run by Ivan Glasenberg, expects as many as four Chinese bidders for a Peruvian copper mine that may be valued at more than US$5 billion. "There are groups forming together and combining," the billionaire chief executive told reporters in London on Tuesday. "We see there will be at least three to four groups bidding. There is some other outside interest besides the Chinese consortiums." There are groups forming together and combining. We see there will be at least three to four groups bidding. There is some other outside interest besides the Chinese consortiums Glencore Xstrata chief executive Ivan Glasenberg A first round of bids is due next week, he said. Chinese companies including Chinalco Mining Corp International, MMG and Citic Resources are among those studying offers for Las Bambas, people with knowledge of the process have said. Glencore, based in Switzerland, is selling the mine as part of an agreement to win Beijing's regulatory approval for its US$29 billion takeover of Xstrata this year. The National Development and Reform Commission, China's top economic planning agency, which approves all major overseas acquisitions, usually restricts state-owned companies from making rival offers. "We understand the NDRC sometimes doesn't allow them to compete, but I think the interest that we've seen in China is very robust," Glasenberg said. "There is very strong interest from some big major groups, and they are not in the consortium, so it seems that they are going to compete." Las Bambas could be valued at more than US$5 billion, a person familiar with the matter said this month. Proceeds from the sale may be returned to shareholders, chief financial officer Steve Kalmin told reporters. About US$3 billion has been spent on the project so far. It is estimated to cost about US$5.9 billion to complete, he said. Xstrata said in January it was building the project at a cost of US$5.2 billion. Glencore, the biggest publicly traded raw-materials supplier, hopes to close the sale by the end of the year, Glasenberg said last month. The deal might not be completed until the first half of next year, Kalmin said this week. The agreement with China struck in April that gave Glasenberg approval to buy Xstrata requires Glencore to sell the mine to a buyer approved by the country's Commerce Ministry by September 30 next year.