British mining giant Rio Tinto is working on a plan to float its US energy coal business, which could fetch a total of around $4 billion (£2.08 billion).

Rio last year said it would sell the business as part of $15 billion of asset sales tied to its purchase of Canadian aluminium producer Alcan.

Rio has lodged a prospectus with the US Securities and Exchange Commission seeking to raise up to $1 billion with a listing of Cloud Peak Energy on the New York Stock Exchange. The offering is underwritten by Credit Suisse.

“Rio Tinto expects to make a final decision on whether to pursue a listing of the shares of Cloud Peak Energy or to pursue another form of divestment once these options have been more fully explored,” the company said.

Cloud Peak is the biggest part of the existing Rio Tinto Energy America business, which is the second-largest US coal producer behind Peabody Energy. Cloud Peak's Powder River Basin mines in Wyoming and Montana supply 11.5% of the US domestic market for coal, generating 6% of US electricity.

Meanwhile, Xstrata's £5 billion hostile bid for platinum miner Lonmin is shaping up as an ill-tempered protracted battle with both sides accusing the other of a dirty tricks campaign.
Xstrata launched the bid last week as a means of becoming a major player in platinum.

Lonmin claimed over the weekend that Xstrata had leaked “false” information to the media suggesting its chief executive, Brad Mills, is facing a boardroom backlash led by chief strategic officer Ian Farmer.

Reports suggest Farmer told Mills he could push for his ousting if performance did not improve.
Xstrata says it is not behind the rumours. It is putting the finishing touches to a £5 billion debt package for the deal with banks including Royal Bank of Scotland, Barclays, Santander and Deutsche Bank.