The European Commission will exclude the over-the-counter derivatives market from its antitrust review of Deutsche Boerse's takeover of NYSE Euronext, undermining a key rationale to gain approval for the deal, three people familiar with the matter said on Monday.

Two sources familiar with Deutsche Boerse's thinking said the European Union's antitrust body signaled it would only look at the market for derivatives traded on an exchange as it assesses the impact of the tie-up.

A person familiar with the European Commission's thinking said it had defined the relevant product market as the exchange-listed derivatives market and not the over-the-counter (OTC) market.

Deutsche Boerse and NYSE Euronext declined to comment. A spokeswoman for EU Competition Commissioner Joaquin Almunia also declined to comment.