* EU antitrust chief sees extended regulatory review of deal
* Warns of anticompetitive risks from one-stop shop model
By Foo Yun Chee
BRUSSELS, March 22 (Reuters) - The EU's antitrust chief highlighted the anticompetitive dangers of a one-stop shop business model, outlining the regulatory hurdles for Deutsche Boerse's bid to acquire NYSE Euronext.
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.
"More open competition, more opportunities, this more open business model, together with interoperability from the competition point of view, is preferred," he said.
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 0.5 percent up at 53.50 euros in mid-session versus a 0.2 percent rise in the Europe Stoxx 600 financial services index. (Editing by Rex Merrifield and Will Waterman)