Nov. 21 (Bloomberg) -- NYSE Group Inc. moved to ease concern among policy makers about its acquisition of Euronext NV by agreeing to split the combined company's board evenly between Americans and Europeans. The stock had its biggest gain since the owner of the New York Stock Exchange went public in March.

NYSE rallied $9.28 to a record $104.60 in composite trading in New York. The 9.7 percent advance was the most since March 8, when the shares rose 25 percent in their first day of trading after NYSE Group merged with Archipelago Holdings Inc. and became publicly traded.

The shares have surged 41 percent this month amid growing optimism that the world's largest equities exchange will gain regulatory and shareholder approval for a merger now valued at $14.6 billion. NYSE will pay for the merger with its own shares and some cash, so the rising stock price makes the transaction more attractive. Deutsche Boerse abandoned its rival bid for Euronext last week, clearing the way for NYSE Group.

``The more the stock goes up, the more likely it is the deal will happen without NYSE having to sweeten its offer, and it just feeds on itself,'' said Thomas Caldwell, chairman of Toronto-based money manager Caldwell Securities, which owns shares in NYSE Group and Euronext.

The board of NYSE Euronext will consist of 11 Americans and 11 Europeans, the companies said in an e-mailed statement today. French Finance Minister Thierry Breton is among policy makers who criticized the joint companies' previously announced governance plans, saying that the deal should be a merger of equals.

Linked Exchanges

The NYSE-Euronext deal would link the Big Board with bourses in Lisbon, Paris, Amsterdam and Brussels and the Euronext.Liffe futures market. Breton's criticisms were supported by Gerard Mestrallet, chairman of Paris Europlace, a French lobby group. Mestrallet last month told a New York audience there needs to be a governance structure ``providing for balanced representation.''

The new board will include the directors of NYSE, members of the Euronext supervisory board, the chief executive of Euronext and another European who will be named later, according to the statement.

The merger originally contemplated a 20-person board, composed of 11 directors from NYSE and nine from Euronext. In September, the board was enlarged to 22 members, with the majority of directors coming from the U.S.

``We had previously shown that we were flexible on this point, and this is something that benefits both organizations and the new company,'' said Richard Adamonis, a spokesman for NYSE Group.

To contact the reporter on this story: Nandini Sukumar in London at nsukumar@bloomberg.net

Last Updated: November 21, 2006 17:22 EST