TOKYO, Sept 26 (Reuters) - U.S. cosmetics and health-care product retailer Neways Inc. is being auctioned in Japan for about $600-700 million, with private equity houses among the bidders, sources familiar with the process said on Tuesday.

Incorporated in 1992, Neways is a multi-layer marketing company that distributes skin-care products and nutritional formulas to 23 countries worldwide.

Neways was founded by Thomas and Leslie DeeAnn Mower. The Mowers, who divorced in July 2000, will start prison terms on Nov. 13 for tax evasion.

Neways, based in Utah County, is being sold due to "personal differences" according to a brief filed by Thomas Mower's lawyers.