Carlyle Group, the second-biggest US private-equity firm, will seek a valuation of $7.5 billion to $8 billion in its initial public offering, according to people with knowledge of its plans.

Carlyle plans to sell a stake of about 10 percent in the IPO and will start marketing the deal to investors as early as next week, said the people, who asked not to be identified because the information is private. The Washington-based firm, which has been gauging public interest since last year, is targeting its share sale in early May, said another person.

At $8 billion, Carlyle would fetch less than half the market value of Blackstone Group LP, the world's largest private-equity firm, which has led an industry push into hedge funds and real estate to reduce its reliance on buyouts.

Carlyle initially sought to convince analysts it deserved a valuation comparable to Blackstone's because its steadier earnings would provide investors with a more stable dividend than most peers', people briefed on the matter said last year.

Chris Ullman, a spokesman for Carlyle, declined to comment.

Carlyle has $147 billion under management, according to the IPO prospectus, and Blackstone had $166 billion as of Dec 31, its filings show. Co-founded in 1987 by David Rubenstein, William Conway and Daniel D'Aniello, Carlyle would be at least the fifth buyout firm to go public since Fortress Investment Group LLC in 2007.

The amount Carlyle is seeking is as much as 25 percent less than the $10 billion implied valuation the firm used when selling debt to Abu Dhabi's Mubadala Development Co in December 2010. The difference in part reflects the firm's desire to attract investors with a price sweetener known as an IPO discount, said the people, who asked not to be named because the information is private.

At the end of last year, Carlyle had an implied enterprise value of about $9.4 billion, according to a regulatory filing on Tuesday. The amount was based on fair value estimates of equity interests tied to Carlyle's 2010 purchase of a majority stake in hedge-fund manager Claren Road Asset Management LLC. Enterprise value calculations include debt as well as market capitalization.

Blackstone, which went public at a market value of $33.5 billion in 2007, has since shrunk by half to about $16.4 billion. The stock has gained 4 percent this year to close at $14.57 in New York on Tuesday. KKR & Co, which gained a New York listing by combining with its publicly traded European fund and moving the company to the NYSE from Amsterdam in July 2010, has risen 30 percent since then.

Carlyle's assets under management have more than tripled since 2006. The 25-year-old firm and rivals such as Blackstone and KKR are lowering fees or offering deals as they vie for investors for their buyout funds.