Nasdaq OMX Group and IntercontinentalExchange Inc took their $11.1 billion takeover bid for NYSE Euronext straight to the exchange operator's shareholders on Monday with a planned tender offer.

The move comes after NYSE's board twice rejected the pair's offer in favor of a $10.3 billion friendly bid by Germany's Deutsche Boerse AG, and it sets the stage for a lengthy battle for the Big Board's future.

The commencement of this exchange offer should convince the NYSE Euronext board of the seriousness of our intentions, Nasdaq Chief Executive Robert Greifeld said in a statement.

Nasdaq and ICE want to split NYSE Euronext's operations between them, and have said theirs is a superior deal for shareholders, who will ultimately have to decide.

NYSE's board has said that unsolicited bid is not serious, it risks being blocked by antitrust regulators, and runs contrary to the company strategy of diversifying internationally. The Deutsche Boerse tie-up would create the world's largest exchange operator.

NYSE Euronext shares were up 1.1 percent at $40.48.

(Reporting by Jonathan Spicer and Paritosh Bansal; Editing by Bernard Orr and Richard Chang)