The U.S. coal business of miner Rio Tinto PLC submitted a new application on Wednesday for an initial public offering of up to $500 million.

The new prospectus, filed by Cloud Peak Energy Inc with the U.S. Securities and Exchange Commission, replaces earlier applications in which it first sought permission last summer to raise up to $1 billion before lowering that to $250 million in October, as the IPO market stumbled last autumn.

Cloud Peak is the third largest U.S. producer of coal and owns surface coal mines in Wyoming and Montana. In 2008, its coal generated about 4.4 percent of the electricity produced in the United States, according to the prospectus.

Cloud Peak had revenues of $360.5 million in the three months ended March 31, 2009, up 19.5 percent over the year earlier period, while net income rose nearly seven-fold to $56.8 million over the same period.

Wyoming-based Cloud Peak has applied to list on the New York Stock Exchange under the symbol CLD.

The prospectus did not indicate the terms of the IPO, including the number of shares to be sold or the potential timing.

The IPO's lead underwriters are Credit Suisse (CSGN.VX), Morgan Stanley (MS.N) and RBC Capital Markets (RY.TO).

(Reporting by Phil Wahba; editing by Carol Bishopric)

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