Deutsche Boerse and NYSE Euronext said they have decided to push back the deadline for completing their merger until March 31.

When they announced the plan to merge in February, the two exchange operators said they expected to complete the deal by the end of 2011.

But their plans have run into headwinds in Europe. The competition commission of the European Union has expressed concern about the part of the combined company that would be involved in derivatives trading and clearing.

The combination of Deutsche Bourse’s Eurex operation with NYSE Liffe would dominate trading in derivatives. The merger partners have proposed several remedies, including the single-name equity derivative business of NYSE Liffe and providing open access to clearing services provided by Deutsche Boerse.

The European Commission is scheduled to decide on the merger by February 9 but competition commissioner Joaquin Almunia said last week a decision on the deal was possible by the end of January, Reuters reported.

NYSE Euronext and Deutsche Boerse control about 90 percent of exchange-based trading in futures and options contracts in Europe.

In a regulatory document filed December 21 with the Securities and Exchange Commission, NYSE Euronext said:

Section 9.2(a) of the Business Combination Agreement provides that each of Deutsche Börse and NYSE Euronext have the right, in its sole discretion, to extend the Termination Date (as defined in the Business Combination Agreement) to March 31, 2012, in the circumstances set forth in such subsection. Deutsche Börse has elected to exercise such right and hereby extends the Termination Date to March 31, 2012.

The exchanges met with officials in Brussels on Dec. 21 to discuss their revised offer, which included capping fees on derivatives trading and clearing for three years, the sale of NYSE’s Liffe single-stock derivatives business, and the licensing of the Eurex trading system to a third party, Bloomberg reported, who declined to be named because the talks are private.

Tom Steinert-Threlkeld writes for Securities Technology Monitor.