The pair are offering $42.50 in cash and stock per Nyse Euronext share, a 19% premium on the Deutsche Boerse proposal agreed in February. For each Nyse share investors are being offered $14.24 in cash, plus 0.4069 shares of Nasdaq OMX stock and 0.1436 shares of ICE.

Under the deal, ICE would take on Nyse Euronext's futures businesses with Nasdaq OMX owning the rest, including exchanges in New York, Paris, Brussels, Amsterdam and Lisbon, as well as the US options business.

In a statement, Nasdaq OMX says a combined firm, headquartered in New York, would create a world leader in market technology, used in over 60 markets internationally.

Nasdaq OMX and ICE are forecasting significant cost savings from a tie-up, with the two New York exchanges moving to a single data centre, and the Nyse Liffe platform switching over to ICE.

Nasdaq OMX CEO Bob Greifeld says a fundamental source of synergies will come from consolidating to a single platform as soon as possible.

In total, Nasdaq estimates $540m in cost savings from the merger, with ICE reaping $200m from integration with Nyse Liffe.

Nyse Euronext and Deutsche Boerse agreed a tie-up in February, part of a wave of consolidation which also saw the London Stock Exchange ink a merger deal with Canada's TMX.

Nasdaq OMX has been expected to try and hijack the deal, with reports emerging last month that it was talking to advisers, led by Bank of America, about a counter-bid for its rival, funded by $5 billion of debt.

Nasdaq OMX's Greifeld, says: "Given that our proposal is clearly a superior proposal, we hope that Nyse Euronext's Board will recognise this opportunity as well as the benefits for Nyse Euronext's employees and customers."

Nyse Euronext shares were up 11.6% at $39.26 in trading before the market opened this morning, according to Reuters.

The Exchange has issued a statement saying it will "carefully review the proposal" and has urged shareholders not to take any action.