EU regulators are reportedly ready to formally offer their objections to the proposed merger of Deutsche Boerse and NYSE Euronext (NYX) this week, the next step for the companies in what has been a lengthy European antitrust review.

The objection by the European Commission is expected to be sent to the parties sometime this week, a source close the matter told Reuters. The NYSE Euronext said on Tuesday that it would not be surprised if the EU objected to the deal. 

An NYSE spokesman said the company was not commenting on the merger or regulation process, however a "statement of objections" is typical of these types of large transactions in the EU and are often provided in cases where the regulator identifies competition concerns. 

After reviewing the statement of objections, the companies are able to offer concessions to ease regulatory concerns and move forward with the deal. The source close to the case declined to provide more information because of its sensitivity, according to Reuters. 

Last month, a German regulatory authority approved the merger in what had seemingly been a step forward for NYSE Euronext and Deutsche Boerse. The companies had said at that time that they “cleared another significant regulatory hurdle” as they worked toward the goal of closing the deal by the end of the year.

However, the transaction remains subject to European antitrust and exchange supervisory approval, which has proven to be the biggest hurdle in the merger.

NYSE Euronext and Deutsche Boerse agreed to merge in February and received shareholder approval in July.

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