Despite recent attempts made by the two exchange operators to arrive at a compromise with European regulators, the transaction will need to overcome more challenges before it reaches approval.

Thus far, NYSE Euronext and Deutsche Boerse have stated in the past that they will not go through with the merger if it means they will need to sell their Eurex and Liffe markets for derivatives, MarketWatch reports. The two firms have tried to minimize their losses by proposing the offloading of smaller assets.

The exchange operators submitted a variety of proposals in November that they hoped would satisfy the regulators, according to The Wall Street Journal. The suggestions included allowing competitors to access the clearinghouse that would be created through the combination and divesting a trade-processing operation.

The media outlet reports that after the latest round of proposals failed to generate a favorable response from the officials, the exchange operators are considering additional measures that could be used to ensure that the merger is cleared. The two companies most recently proposed divesting overlapping portions of their European derivatives business and letting competitors access the Eurex clearinghouse.