A $17 billion New York Stock Exchange merger was in doubt Wednesday after European regulators urged rejection of a deal with a German securities exchange. The chief executives of NYSE Euronext and Deutsche Boerse were to meet in New York Wednesday to discuss the next steps in the proposed Deutsche Boerse takeover of NYSE Euronext, a day after European antitrust regulators said they opposed the deal, worked out 11 months ago, The Wall Street Journal and New York Times reported. A successful deal would create the world\'s largest stock exchange operator with a market capitalization of listed companies equal to $15 trillion. About $13.39 trillion of that would come from NYSE Euronext, which is about six times Deutsche Boerse\'s size. The recommendation by the European Union\'s antitrust commission staff, which was not made public as of early Wednesday, cited the potential power of a combined Deutsche Boerse and NYSE Euronext over the trading of exchange-listed derivatives, including futures and options, the newspapers said. A derivative is a security whose price is dependent on, or derived from, one or more underlying assets. The underlying assets often include stocks, bonds, commodities, currencies, interest rates and market indexes. Most derivatives are highly leveraged to amplify returns. The two exchange operators still have until early February to change commissioners\' minds. The commissioners are to discuss the deal Feb. 1 and make a final decision by Feb. 9. NYSE Euronext, Deutsche Boerse and European Commission antitrust division representatives had no immediate comment. The 27-person commission, the EU\'s executive body, must still make a ruling, but only about 10 percent of mergers that undergo an in-depth EU review are approved after a recommended block by antitrust examiners, Toronto financial-services provider BMO Capital Markets says. The NYSE-Deutsche deal received conditional U.S. regulatory approval Dec. 22, provided a Deutsche Boerse subsidiary divested its 31.5 percent interest in No. 3 U.S. stock exchange Direct Edge of Jersey City, N.J. A hostile bid for NYSE Euronext put forth by Nasdaq OMX Group Inc. and the futures exchange operator IntercontinentalExchange Inc. was dropped last May after the suitors received notice from U.S. antitrust officials they would oppose the rival deal.