IntercontinentalExchange Inc and Nasdaq OMX have no reason to boost their takeover bid for the New York Stock Exchange parent company because their joint offer is already superior, ICE's chief executive said on Tuesday.

On Sunday, NYSE Euronext directors rejected the unsolicited $11.3 billion bid from ICE and Nasdaq in favor of a friendly tie-up deal with Deutsche Boerse, worth about $10 billion.

Asked on Tuesday whether the pair would now boost their offer, ICE CEO Jeffrey Sprecher said: We have no reason to because it's a superior offer.

We think the proposal has merits so we will continue that process, Sprecher told reporters in Rio de Janeiro, where he attended an exchange conference. Both Nasdaq and ICE have received an excellent response from NYSE shareholders on the bid, he added.

Stock exchanges globally are maneuvering to bulk up and break into new, more profitable asset classes.

The battle for NYSE Euronext -- which runs stock and futures markets in the United States and across Europe, and is the largest of the takeover targets -- has in the last week got increasingly bitter.

Though NYSE's directors unanimously dismissed the ICE-Nasdaq bid as strategically unattractive, with unacceptable execution risk, Sprecher said he wants to maintain friendly conversations with both NYSE management and shareholders.

We continue to talk to shareholders and ultimately they will decide. There's a continuing shareholder dialogue, added Sprecher, who earlier on Tuesday said Atlanta-based ICE plans to expand into Brazil by opening a marketplace for power contracts.

(Reporting by Brian Ellsworth; Writing by Guillermo Parra-Bernal and Jonathan Spicer; Editing by Lisa Von Ahn and Tim Dobbyn)