By Jonathan Spicer

NEW YORK (Reuters) - The New York Stock Exchange, an icon of American capitalism, is expected to take a crucial step toward ceding control to a German company on Thursday, with little opposition expected from investors.

NYSE Euronext shareholders are voting on whether to back a $9.4 billion takeover of the company that owns the NYSE by Deutsche Boerse AG. The deal is expected to get the needed 50 percent majority support from investors, including T. Rowe Price and other big U.S. fund companies.

The vote is set to begin at 8:00 a.m. Eastern.

The exchanges have promoted the deal as a merger of equals -- in part because it allows Big Board Chief Executive Duncan Niederauer to run the combined entity. The larger Frankfurt-based bourse, however, would control 10 of 17 board positions, while its shareholders will own roughly 60 percent of a yet-to-be-named Netherlands-based holding company.

If roadblocks to the blockbuster deal emerge, they are likely to come from Europe. The deal requires approval from 75 percent of Deutsche Boerse shareholders by Wednesday of next week and then would have to survive a thorny European Commission antitrust review that could run through the rest of the year.

The tie-up between NYSE and the German exchange was announced in February amid a flurry of cross-border deal attempts by exchanges eager to cut costs and diversify in the face of fast-eroding market shares in their traditional stock-trading businesses.

NYSE Euronext itself was the target of an unsolicited counter-bid in April from archrival Nasdaq OMX Group Inc and its commodities partner, the IntercontinentalExchange Inc in April. The aggressors retreated in May after being rejected by the U.S. Department of Justice over antitrust concerns.

A NYSE-Deutsche Boerse combination would produce a behemoth that offers trades in virtually every U.S. and European asset class, with annual trading volume exceeding $20 trillion. It also explains why European antitrust regulators are expected to take a close look at the near lock the company would have on exchange-traded derivatives -- and possibly demand some divestitures or other concessions.

There have been few public critics of the deal in the United States, despite the NYSE's symbolism as a bastion of American capitalism. The exchange was founded in 1792 when share trading began under a buttonwood tree on a block now designated as Wall Street.

To woo votes, Niederauer and his Deutsche Boerse counterpart, Reto Francioni, have been telling shareholders they expect to achieve cost savings from the combination of at least 500 million euros ($715 million), ramped up from an initial projection of 300 million euros ($429 million). They also have promised a special dividend of 2 euros per share ($2.86 per share) after the deal closes.

Under the terms of the deal, Francioni would be chairman of the combined entity.

NYSE shares are up nearly 15 percent this year, but have fallen about 9.7 percent since the exchange said it was in advanced talks on February 9. Deutsche Boerse shares are down 8.9 percent since February 9 and up 2.8 percent year to date.

(Reporting by Jonathan Spicer; additional reporting by Paritosh Bansal; editing by Jed Horowitz and Andre Grenon)