Private equity firm Apollo Global Management LLC lowered the expected range for the price of its initial public offering after delaying its filing as a nuclear crisis in Japan and democracy protests in the Middle East rocked markets.

Apollo filed on Monday with U.S. regulators to sell 26.3 million shares for $17 to $19 each. Sources previously told Reuters the company planned to sell the stock at $18 to $20. The filing to sell shares at that price range was expected last Tuesday, the sources said.

But last week, Apollo delayed its $500 million IPO, days after the devastating earthquake in Japan, which rattled U.S. stock markets and raised concerns volatility could also hurt demand for new issues.

IPOs globally, including Danish cleaning and cooking services provider ISS , were postponed as the nuclear crisis in Japan continues to unfold and how long it will take to resolve remains unclear.

The Standard & Poor's 500 and Dow Jones Industrial average stock indexes recently suffered losses that briefly erased their 2011 gains. But in what could be an early sign of a turnaround, the indexes ended last week with a two-day rally and each rose 1.5 percent and on Monday.

If it goes public, Apollo will join Kohlberg Kravis Roberts & Co LP and Blackstone Group LP as one of the few publicly traded private equity firms.

If successful, Apollo's IPO could clear the way for other alternative asset managers such as Carlyle Group , TPG Capital LP and Oaktree Capital Management LP to go public.

Its IPO will follow closely on the heels of the successful buyout-backed flotations of Nielsen Holdings NV, Kinder Morgan Inc, BankUnited Inc and HCA Holdings Inc.

The pricing of Apollo's IPO is expected to take place after the market closes on March 29 or 30, according to a market source who spoke on condition of anonymity because the information is not public.

The offering has been in the works since 2008 and it remains unclear what prompted Apollo to propose IPO terms just a few days after sources said the company would wait for markets to settle.

At the midpoint of the proposed price range, the IPO would give Apollo a market value of about $6.4 billion.

Apollo's $67.6 billion in assets under management include investments in companies such as casino operator Caesars Entertainment and real estate company Realogy.

The company was founded in 1990 by former Drexel Burnham Lambert banker Leon Black. He and his partners will retain control of 80.7 percent of the voting power.

Apollo will sell 18.0 million of the 26.3 million shares in the IPO. It said it would use proceeds from the offering for general corporate purposes and to fund growth. Existing stockholders will sell the remaining 8.3 million shares.

Goldman Sachs Group Inc , which is selling 2.7 million of its 4.7 million Class A shares, is also leading the underwriters, alongside JPMorgan Chase & Co and Bank of America Merrill Lynch .

Apollo plans to list its shares on the New York Stock Exchange under the symbol APO . They currently trade on Goldman's private stock exchange, GSTrUE.

Separately, Apollo Residential Mortgage Inc -- a residential real estate finance company managed by Apollo Global's indirect subsidiary -- also filed for an IPO on Monday, looking to raise up to $300 million.

(Additional reporting by Clare Baldwin; Editing by Gerald E. McCormick, Gunna Dickson, Lisa Von Ahn, Andre Grenon, Steve Orlofsky and Carol Bishopric)