Nasdaq Stock Market Inc has agreed to buy the Philadelphia Stock Exchange, which operates the third-largest U.S. equity options market, for about $650 million, two people familiar with the matter said on Tuesday.

Nasdaq edged out bigger rival NYSE Euronext and other bidders in a weeks-long race to buy PHLX in what is likely to be an all-cash deal, sources said.

Nasdaq, which is expected to launch its own options market in December, will buy PHLX, the nation's oldest securities exchange, with cash raised from the recent sale of its 30 percent stake in the London Stock Exchange, one person familiar with the matter said.

Nasdaq is likely to pay about $650 million for PHLX, but a deal has not yet been finalized, sources said.

Television news network CNBC initially reported that Nasdaq was buying the exchange for $500 million.

Sandy Frucher, chief executive of the privately owned PHLX, and Nasdaq spokeswoman Silvia Davi had no comment.

Nasdaq and PHLX have previously talked about a deal, according to press reports.

The Philadelphia exchange trades stocks, options and currencies, but its recent growth has been driven by its options business.

PHLX has about 15 percent of the U.S. options trading market, which has seen explosive growth in recent months.

(Reporting by Anupreeta Das)

NYSE Euronext Investment London stock exchange NASDAQ OMX Group