Nasdaq OMX Group Inc told investors it could sell NYSE Euronext's American Stock Exchange and offer a break-up fee to overcome antitrust concerns in its $11.3 billion bid for the Big Board parent, a source familiar with the situation said on Friday.

Nasdaq, along with IntercontinentalExchange Inc , has made a rival offer for NYSE Euronext, which already has a $10.2 billion deal to merge with Deutsche Boerse .

NYSE Euronext has rejected the Nasdaq/ICE offer as too risky and unattractive, and on Friday Nasdaq Chief Executive Robert Greifeld met hedge fund managers to make his case.

A Nasdaq spokesman was not immediately available for comment late on Friday. The source asked not to be named because these discussions are not public.

Greifeld and his counterparts at NYSE Euronext and Deutsche Boerse, Duncan Niederauer and Reto Francioni, have all been meeting NYSE shareholders, who are expected to vote on the German tie-up in July.

Although both deals face considerable antitrust hurdles, some investors have said Greifeld needs to make a strong case he can overcome a regulatory review.

Combining Nasdaq and the NYSE would bring the top two U.S. stock exchanges together with a virtual monopoly on listings, and dominance in trading U.S. cash equities and options.

NYSE Amex lists small and micro-cap stocks, and is an important part of the company's options business. It was bought by NYSE in 2008.

The idea to sell Amex came up as a possible solution should divestitures be required due to antitrust concerns, the source said.

But a source close to NYSE said selling Amex will not solve the antitrust issue in a deal with Nasdaq.

Amex is fully integrated with NYSE and no longer a separate listing venue, the source close to the Big Board said, adding that Amex was not an effective competitor in the listings business even when it was bought by NYSE.

Greifeld told investors he hoped to get some guidance from antitrust regulators in the next six or seven weeks, according to the Wall Street Journal, which first reported the news.

To allay antitrust concerns, Nasdaq could also cut annual listing fees for the largest companies by $50,000 to $450,000 and agree to cap fees on others for a while, the paper reported.

(Reporting by Paritosh Bansal and Jonathan Spicer; Editing by Tim Dobbyn and Richard Chang)

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