Rio Tinto Group, fending off a $100 billion hostile offer from BHP Billiton Ltd., expects to sell coal and uranium assets in the second half of the year and has been approached by about a dozen possible bidders.

Rio said in November it may sell the Sweetwater and Kintyre uranium deposits in the U.S. and Australia, and its Energy America unit, which owns five coal mines. They are part of $30 billion of assets put up for sale to repel BHP and finance the acquisition of Canadian aluminum producer Alcan Inc.

"I'd be happy with nine months and I'd start to worry if it were 12 months'' before a sale of the three energy assets takes place, Preston Chiaro, the head of Rio's energy unit, said in an interview in London yesterday. There have been about a dozen possible bidders for the uranium deposits, "expressions of interest'' for the coal mines and a final decision on whether to sell the assets will depend on the offers made, he said.

BHP in November said it may offer three shares for every share of London-based Rio, which rejected the approach. The Melbourne-based company must formalize its offer by Feb. 6 or walk away, the U.K. Takeover Panel ruled. The combined entity would be the biggest producer of thermal coal and copper.

Those that have expressed an interest in the uranium and coal assets include mining companies and private equity firms, Chiaro said.

Rio rose 360 pence, or 8.7 percent, to 4,519 pence in London. The stock has gained 64 percent in 12 months, compared with a 44 percent advance for BHP Billiton.

Australian prices for thermal coal, burned by power plants, should remain "high'' through the rest of the year, Chiaro said. Coal from Newcastle port in Australia reached a record $91.77 a ton in the week ended Jan. 4.

Rio's energy unit accounted for 16 percent of sales in 2006, compared with about 18 percent in 2005 and 19 percent in 2004, Bloomberg data show. Rio is the world's third-biggest mining company and BHP is the largest.

Prices for coking coal, used by steelmakers, may be "even more extreme,'' Chiaro said. Semi-soft coking coal for immediate delivery has traded at $140 a metric ton, twice its price a year ago, he said. Better quality hard coking coal has traded at "well over'' $200 a ton, he said.

"I don't think those spot prices are going to be the long- term contract prices,'' Chiaro said. "We see upward movement but I can't give you a number. It's a very strong market for sellers.''

Coking and thermal coal is usually sold at benchmark prices set annually for the Japanese financial year starting in April. Chiaro said he's "pretty confident'' the "difficult'' talks will be completed by April 1.

Rio is targeting more uranium production from its Ranger mine in Australia's Northern Territory this year, Chiaro said.

The company is also "looking at yet another extension of the Ranger pit,'' he said. ``We hope to be able to announce something on that this quarter.''