Nasdaq OMX Group Inc. (NDAQ) is moving forward with plans to launch a third U.S. equities exchange next year that will incorporate a new pricing model for stock trades, the company announced Thursday.

The new platform will use an exchange license acquired via Nasdaq OMX's 2007 purchase of the Philadelphia Stock Exchange, and is intended to give investors "additional choices that will help supplement their various trading strategies," Executive Vice President Eric Noll said in a statement.

It also gives the transatlantic exchange operator another tool to regain market share in U.S. cash equities, where smaller electronic rivals have cut into Nasdaq OMX's business.

The new platform, not yet named, is slated to launch in the second half of 2010, pending approval from the Securities and Exchange Commission.

Nasdaq OMX shares fell 19 cents in recent trading to $20.60. The stock is down 17% this year.

The company is working to diversify as upstarts BATS Exchange and Direct Edge now claim more than one-fifth of U.S. stock trading activity, chipping away at a business long dominated by Nasdaq OMX and NYSE Euronext (NYX).

Nasdaq OMX said the new platform will feature a price/size priority model that will allow customers to execute orders through any of Nasdaq's platforms, as opposed to the price/time priority model offered on the Nasdaq Stock Market and Nasdaq OMX BX.

The announcement of the new Nasdaq OMX platform comes as its junior BX platform has gained traction in recent months, with the help of a money-losing price plan that lifted its market share to 2.6% in August.

Business at BX rose further to an estimated 3.2% in September, even after Nasdaq OMX raised prices.

The new exchange is among a host of new ventures being pursued by Nasdaq OMX Chief Executive Bob Greifeld as the company works to diversify.

On Wednesday, Nasdaq OMX announced a new listing market aimed at smaller companies that don't currently qualify for listing on the Nasdaq Stock Market or the New York Stock Exchange, which it is calling BX.

"With BX we are filling a necessary need for a well-regulated listing venue for companies that otherwise would transfer to, or remain on an unregulated or lightly regulated platform," said Bob McCooey, senior vice president of Nasdaq OMX, in a statement.

The move puts Nasdaq OMX up against OTCQX, a platform operated by Pink Sheets operator Pink OTC Markets Inc. (PINK), and Toronto-based TMX Group (X.T)'s Venture Exchange.

Both venues aim to serve as a stepping stone toward listing on a bigger market, and target startup companies alongside those that have been delisted after falling below standards for market capitalization or share price.

Companies looking to list on BX will need to meet some listing requirements, like having three or more independent directors and an independent audit committee, according to Nasdaq OMX.

BX will leverage a listing license held by the Boston Stock Exchange, acquired by Nasdaq OMX in September 2008. That platform's launch also requires SEC approval.

-By Jacob Bunge, Dow Jones Newswires; 312-750-4117; jacob.bunge@dowjones.com

(Mike Barris contributed to this report.)