* EU's Almunia says deal is a "complex" case
* Antitrust experts say derivatives activities a concern
* Antitrust clearance seen easier in U.S.
By Foo Yun Chee
BRUSSELS, March 10 (Reuters) - EU regulators are likely to take a long, hard look at Deutsche Boerse's planned takeover of NYSE Euronext, the EU's antitrust chief said, with dominance in derivatives seen as a key focus.
EU Competition Commissioner Joaquin Almunia's comments on Thursday underscored the hurdles the deal faces in Europe compared with the United States where regulators were expected to clear the $10.2 billion takeover.
"This is a complex case," Almunia told Reuters on the sidelines of an International Bar Association conference.
"The NYSE Euronext deputy chief executive has recognised this before his meeting with me, it probably will require a deep investigation," he said. "We are waiting for the notification."
NYSE Euronext Deputy Chief Executive Dominique Cerutti met Almunia last month. A NYSE Euronext spokeswoman said the exchanges plan to formally file the deal with regulators in due course. Recent media reports cited Cerutti as suggesting an April filing.
Antitrust experts said the merged group's dominance of exchange-based European derivatives trading -- such as swaps tied to interest rates or government bonds -- is expected to face intense regulatory scrutiny.
Trading and clearing derivatives will be the main source of income for the new group, accounting for 37 percent of total revenues, based on 2010 figures, with most of it coming from Europe.
Another area of potential concern is the link between the exchanges and Deutsche Boerse's derivatives clearing house, Eurex, and the danger that a merged group could stifle new entrants by restricting access to Eurex.
Clearing is becoming increasingly important as regulators require over-the-counter (OTC) swap deals to be cleared centrally.
The antitrust watchdog will also need to take into account regulators' efforts to move trading of OTC derivatives onto exchanges.
Europe's exchanges are bulking up as part of a global trend to consolidation of securities markets and trading systems.
The London Stock Exchange, Europe's largest stock exchange by value of daily trading, agreed a takeover deal with Canadian exchange TMX Group on Feb. 9.
And just a few days later, U.S.-based exchange operator BATS Global Markets agreed a deal to take over trading platform Chi-X Europe in a move that could further increase pressure on national bourses.
(Editing by Rex Merrifield and Elaine Hardcastle)