The EU's antitrust chief reiterated today that the proposed merger of Deutsche Boerse and NYSE Euronext is likely to face a lengthy regulatory review that could take until the end of the year.

The European Commission is currently assessing the $9 billion deal and has set an August 4th deadline for the preliminary review.

"Probably we will need phase two, as I announced months ago. We will continue working until the end of this year," EU Competition Commissioner Joaquin Almunia told a news conference.

A phase two review could take an additional 90 to 105 working days.

Mr Almunia said in March he expected to take a long, hard look at the takeover, as it was a complex case. He has also stressed the risks of a one-stop shop business model, saying he preferred an open system and interoperability.

The proposed deal has stirred concerns that the combined group's 94-per cent share of listed derivatives trading in Europe due to its captive clearing and settlement operations could thwart competition.

Some opponents have called for such vertical "silos" to be broken up. Shareholders of NYSE and Deutsche Boerse have already approved the deal.

Reuters