Nasdaq’s Robert Greifeld has put the American company’s substantial stake in the London Stock Exchange up for sale.

The move is thought to signal the end of the aggressive CEO’s ambitions to take over the LSE, while giving him extra leverage in his bid for the Scandinavian exchange group, OMX.

The sale would open the way for a higher offer on OMX, after the Dubai Financial Centre topped Nasdaq’s agreed bid last week.

Speculation is rife that a deal between Nasdaq and Dubai may be in the offing, which would leave the ambitious Gulf State with a major holding in the LSE and Greifeld with a clear run at OMX.

That would be yet another blistering headache for Clara Furse and her team in the City.

The Dubai stock exchange is seeking approval from the board of OMX, the pan-Scandinavian stock exchange group, to support a £2 billion ($4bn) takeover offer this week.

The Dubai International Financial Centre (DIFC), which owns the exchange, has set up meetings with key shareholders of the Swedish-based group and its management, to pave the way for a bid of around 230 kronor (£16.70) per share. Bankers at HSBC, which is advising the Dubai owners, seem to have suggested privately that the Emirate was prepared to pay as much as 250 kronor a share.

They will also have meetings with members of the Swedish government and regulators in an attempt to win support for the approach.

These moves could have implications for the London Stock Exchange. Dubai is thought to have plans to create a pan-European exchange to include the LSE and its new partner, Borsa Italiana. Such a grouping would rival NYSE/Euronext, which was formed last year.

Nasdaq’s recently-agreed bid of £1.8 billion ($3.6bn) for OMX now looks weak in comparison. However, talk of Dubai approaching the American exchange to be part of its masterplan seem wide of the mark. Dubai is shy of a political backlash if it buys in America again, following turbulence created by its recent purchase of P&O and its American ports.

Nasdaq chief executive, Bob Greifeld, last week told investors that its funding for the OMX bid was “flexible”. Insiders are apparently saying that “all options” were on the table, including selling some of Nasdaq’s 22 percent stake in the London Stock Exchange.

A source is quoted as saying, “Greifeld is determined to get this and is leaving no stone unturned. He is also aware that his future is uncertain if this bid fails, after the failure of the London Stock Exchange bid.”

With a place in the FTSE 100 now assured, Clara Furse may be on the prowl again for another asset to bolster LSE independence from Dubai’s predatory instincts.

Investors in the London Stock Exchange have backed its bid to take over Borsa Italiana by a large majority. Some 78 percent of the shareholder base approved the deal, including Nasdaq, former hostile bidder for the LSE which holds 30 percent of the shares.

Chief Executive, Clara Furse said, “This value-creating deal also accelerates our shared vision to become the world’s capital market”.

The Borsa brings a welcome strength in derivatives and fixed-income trading to an often beleaguered London market that let slip the chance to buy Liffe five years ago. The deal will put the LSE in the Footsie 100 for the first time.

It will now be more difficult for any predator wishing to snap up the LSE in future. Nasdaq’s agreement may signal it now accepts that future bids are out of the question.