A proposed merger by NYSE Euronext with Deutsche Boerse has been blocked by the EU on competition grounds.
The proposed deal would have created the world's largest stock exchange operator.
However, the European Commission blocked the deal because it said it would have created a "near monopoly" in European financial derivatives.
NYSE Euronext and Deutsche Boerse said they would now end the deal, which was announced in February last year.
NYSE said it would now resume a $US550 million share buy-back programme.
The European Commission said the planned tie-up would have controlled more than 90% of global trade in European financial derivatives.