NYSE Euronext sees cost savings in its $9.8 billion deal with Deutsche Boerse at closer to 400 million euros ($580 million), up by about a third from its initial estimate, according to a Big Board spokesman on Sunday.

NYSE Chief Executive Duncan Niederauer also sees the biggest NYSE and Deutsche Boerse customers saving at least $3 billion from the combination of their European derivatives platform, according to spokesman Richard Adamonis.

Adamonis was confirming comments made earlier by Niederauer in an interview with the Financial Times.

The new cost savings estimate, along with a 100 million euro ($145 million) revenue synergy expectation, would bring the total synergies from the deal to about $725 million, closer to the estimates from a competing takeover offer.

Nasdaq OMX Group Inc and IntercontinentalExchange Inc have launched a rival $11.2 billion takeover bid for NYSE Euronext. That deal promises net synergies of $740 million.

Last week, NYSE's board rejected the Nasdaq/ICE bid for the second time in 11 days.

All four exchanges involved in the increasingly bitter takeover battle are trying to persuade NYSE shareholders to back their deal.

Niederauer's comments come ahead of a closely watched NYSE shareholder meeting on April 28 for their annual vote on the company's directors.

The vote on the Deutsche Boerse deal is expected on July 7, according to Niederauer's comments, confirmed by his spokesman.

(Reporting by Paritosh Bansal, editing by Bernard Orr)