Nasdaq to Buy Philadelphia Stock Exchange

The Nasdaq Stock Market has agreed to acquire the Philadelphia Stock Exchange for $500 million to $600 million, CNBC has learned.

Rumors of the acquisition plan have been rife since earlier this year, after the Nasdaq had bid $4 billion for Sweden's OMX exchange.

But the takeover attempt was stymied by a counterbid from the United Arab Emirates' stock exchange, the Dubai Bourse -- which then dropped its own bid in exchange for 20 percent of the Nasdaq as well as the U.S. exchange's 28 percent of the London Stock Exchange.

Analysts suggest that the Philadelphia purchase means that the Nasdaq is expanding into options.