Nasdaq OMX is close to launching a hostile bid for NYSE Euronext - which has an office in Belfast - after the rival exchange group repeatedly refused to open talks on its $11bn (£6.6bn) takeover offer.
The direct appeal to NYSE shareholders could come as early as this week as Nasdaq works to prise the NYSE board from its commitment to an alternative deal to sell the company to Deutsche Borse.
The battle for control of NYSE, parent company of the New York Stock Exchange and the Liffe derivatives market in Europe, has become increasingly bitter, as Nasdaq accused NYSE of flouting the corporate governance rules it imposes on companies listed on its exchange.
Bob Greifeld, chief executive of Nasdaq, attacked the NYSE board for refusing to talk to him about his alternative proposal, which is worth more than the deal on the table from Deutsche Borse.
Nasdaq has teamed up with IntercontinentalExchange, a fast-growing derivatives exchange, to make a joint bid for NYSE, and the two companies will carve up the NYSE business between them if they are successful.
NYSE shareholders would get $3.7bn (£2.2bn) in cash, plus Nasdaq and ICE shares, making the total value of the deal $11.1bn at yesterday's prices.
Nasdaq and ICE were last night working on the details of a tender offer for NYSE shares, in which NYSE investors could register their intent to accept the offer - a move that would bypass the NYSE board.
Last year NYSE Technologies, the technology arm of NYSE Euronext, opened new premises in Belfast where it plans to increase its workforce to 400.
At NYSE's annual shareholder meeting last week, investors called for the opening of talks with Nasdaq, in the hopes of generating a bidding war. NYSE shareholders will get a little under half of the combined group in the all-share merger with Deutsche Borse, which values NYSE at $10.3bn (£6.1bn).
When Nasdaq launched its counter-bid for NYSE last month, it was valued at a 21% premium to the Deutsche proposal, but that enticement has eroded. Because of the falling dollar and a rise in the Deutsche Borse share price, Nasdaq's proposal is now worth less than 8% more.
Duncan Niederauer, NYSE chief executive, defended the Deutsche Borse tie-up, which will create the world's largest exchange group. Analysts say both proposals face competition hurdles. NYSE described Nasdaq's bid as "an empty vessel" that could not be approved by US anti-trust authorities.