Nasdaq OMX Group Chief Executive Robert Greifeld, unbowed after NYSE Euronext twice rejected his takeover offer, is pressing forward with a hostile bid for the Big Board parent, promising to launch a tender offer within weeks.

NYSE's board has refused to meet with Nasdaq and IntercontinentalExchange Inc to discuss their offer, sticking instead with an existing deal with Deutsche Boerse AG .

But NYSE has an obligation to talk to Nasdaq and ICE, which values NYSE at $1.3 billion more than the Deutsche Boerse deal, Greifeld said in slides presented at a UBS financial services conference in New York.

Greifeld and ICE CEO Jeffrey Sprecher, who first proposed to buy NYSE on April 1, have repeatedly called on NYSE shareholders to demand that NYSE at least meet with them, most recently in a letter on Monday that suggested NYSE shareholders are being railroaded into an inferior deal.

Nasdaq is working at a rapid pace to clear antitrust hurdles with the U.S. Department of Justice, Greifeld said on Tuesday. The combination of NYSE and Nasdaq would create a near monopoly in the U.S. stock-listing business, and the DOJ would likely ask for some remedies, Greifeld said.

Any such concessions would not change the basic business plan for the merger, he said, adding that he would expect increased U.S. Securities and Exchange Commission oversight as well as competition from smaller upstarts should the combination be approved.

Underscoring its confidence in the talks, Nasdaq's offer includes a $350 million payment to shareholders should antitrust authorities block the deal.

NYSE's agreement with Deutsche Boerse has no such fee, even though it faces intensive scrutiny from European regulators.

Earlier this month, Nasdaq and ICE said they planned to take their bid directly to shareholders in a tender offer.

Greifeld on Tuesday reiterated that promise, saying the offer is still probably a couple weeks away.

NYSE shareholders are scheduled to vote on the Deutsche Boerse deal on July 7 under a timeline that NYSE says is designed to comply with German law on mergers and acquisitions.

But Greifeld suggested he is nowhere close to giving up. We are here for the end game, he said.

(Reporting by Ann Saphir; Editing by Tim Dobbyn and Gerald E. McCormick)