* EU antitrust chief sees extended regulatory review of deal
* Warns of anticompetitive risks from one-stop shop model
(Adds Deutsche Boerse no comment, lawyer, updates shares)
By Foo Yun Chee
BRUSSELS, March 22 (Reuters) - Deutsche Boerse AG's bid to acquire NYSE Euronext faces a hard regulatory battle after the EU's antitrust chief highlighted the anticompetitive dangers of its one-stop shop business model.
Deutsche Boerse unveiled its $10.2 billion takeover of NYSE Euronext last month to form the world's largest exchange operator, part of a wave of tie-ups in the increasingly competitive and global exchange world.
The merged group would dominate exchange-based European derivatives trading, with operations spanning the United States, Germany, France, Britain, the Netherlands, Portugal and Belgium.
EU Competition Commissioner Joaquin Almunia said he was concerned about the "vertical silo" business model such as that of Deutsche Boerse, under which the company owns the exchange, a clearing house and a depository.
"From the competition point of view, I tend to prefer models that are not a vertical silo," Almunia told a European Parliament hearing on Tuesday.
"More open competition, more opportunities, this more open business model, together with interoperability from the competition point of view, is preferred," he said.
THINK ABOUT SOLUTIONS
Deutsche Boerse declined to comment. The Chicago Mercantile Exchange, the world's largest derivatives marketplace and the main competitor to NYSE Euronext, also has clearing and settlement as part of its portfolio.
Antitrust lawyers said Almunia appears to be sending a message to Deutsche Boerse and NYSE Euronext.
"It seems to be about derivatives. Almunia seems to be saying that the companies need to think about solutions while they are preparing the notification," said Morten Nissen, a Brussels-based partner at law firm Bird & Bird.
Almunia said he expected a long, hard look into the takeover once it is notified formally to the European Commission, reiterating comments he made to Reuters earlier this month.
"I will not be surprised -- I cannot anticipate, but I will not be surprised -- if this merger, once it is notified, will be one of those cases where we are obliged to go to phase 2," he said.
The Commission, which acts as competition regulator in the 27-member European Union, takes 25 working days for the first phase of reviewing a deal.
A detailed second-stage investigation can take up to 90 additional working days, and the Commission may extend this to 105 working days if companies offer commitments to address any competition concerns.
Deutsche Boerse shares were trading 0.3 percent down at 53.12 euros by 1440 GMT versus a 0.1 percent drop in the STOXX Europe 600 financial services index. (Additional reporting by Ed Taylor in Frankfurt; Editing by Rex Merrifield and Elaine Hardcastle)