UPDATE 1-American Water Works files with U.S. SEC for IPO

(Adds background, financials, offering details)

WASHINGTON Aug 27 (Reuters) - American Water Works Co Inc, a wholly owned subsidiary of Europe's third-largest utility RWE (RWEG.DE), filed with U.S. regulators on Monday for an initial public offering of up to $1.5 billion in common stock.

The water and wastewater utility company said in a registration statement with the Securities and Exchange Commission that Goldman Sachs & Co, Citi, and Merrill Lynch & Co were underwriting the IPO.

American Water Works plans to list its shares on the New York Stock Exchange under the symbol "AWK" (AWK.N).

The Voorhees, New Jersey-based company did not disclose an estimated price for shares, and said all of the stock in the public offering was being sold by Thames Water Aqua Holdings GmbH, a direct wholly owned subsidiary of RWE.

The filing also did not disclose how many shares Thames Water Aqua Holdings planned to sell in the offering. Those details are expected in future filings.

American Water Works said it would not receive any proceeds from the IPO, and it did not say in the filing what Thames Water Aqua Holdings would do with the funds.

American Water Works also said it would be offering equity units in a separate prospectus but that its IPO was not contingent upon the consummation of its equity unit offering.

RWE said in the past it planned to sell a majority in American Water, bought in 2003 for $4.6 billion excluding debt, by the end of the year as investments in water grids draw away money from growing energy markets.

As part of its strategy to exit water businesses outside continental Europe, last October RWE sold British water utility Thames Water for $9.68 billion excluding debt.

According to the SEC filing, for the six months ended June 30, American Water earned $52.41 million from continuing operations on $1.03 billion in operating revenues.

For the year-earlier period, the company earned $28.16 million from continuing operations on $1.01 billion in operating revenues. (Reporting by Karey Wutkowski) (Additional reporting by Peter Dinkloh in Frankfurt)