Deutsche Boerse and the London Stock Exchange agreed Wednesday to press ahead with their planned merger to create one of the world's biggest exchanges, insisting the tie-up will succeed irrespective of the outcome of the looming Brexit vote on Britain's future in the EU.

The two operators said that they planned to proceed with their "merger of equals" under the key terms already drawn up.

The announcement comes as US-based global markets operator Intercontinental Exchange (ICE), which owns the New York Stock Exchange, is also mulling a rival bid for the LSE.

And it comes at a politically sensitive time as Britain is due to hold a referendum on June 23 to determine whether it remains in the European Union.

It is the third tie-up attempt after two earlier failed bids in 2000 and 2004.

Deutsche Boerse chief executive Carsten Kengeter told a telephone news conference that the tie-up was "the right transaction at the right time for both of our companies. Deutsche Boerse and LSE are the right fit."

The combination will "deliver more than the sum of its parts", he added.

And LSE chief Xavier Rolet said that he "100-percent backed" the plans, but neither made any reference to ICE's rival offer.

- No threat from Brexit -

Kengeter and Rolet insisted that the plans would not be torpedoed even if Britain votes to leave the EU.

"The company and the structure of the transaction is such that we'll have a successful merger irrespective of the outcome," said Kengeter.

A committee has been set up to examine the implications of any vote to leave, but it "would not renegotiate terms, just provide answers," he added.

As already proposed at the end of last month, Deutsche Boerse shareholders will end up with 54.4 percent of the new holding company's capital, and LSE shareholders with 45.6 percent.

Both markets would continue using their current brand names.

The LSE and Deutsche Boerse are to become intermediate subsidiaries of the combined group, with the existing regulatory framework to remain unchanged.

The combined group would have headquarters in London and Frankfurt and the board would have "equal representation" from both sides.

LSE chairman Donald Brydon will be chairman of the combined group and Deutsche Boerse chief executive Kengeter will assume the role of CEO while LSE's finance chief David Warren will be chief financial officer.

- 'World's biggest' -

The two sides described it as an "industry-defining combination" that would create a "leading Europe-based global markets infrastructure group".

In addition to the London market, LSE also operates the Milan stock exchange and LCH Clearnet transaction clearing house. Deutsche Boerse operates the Frankfurt exchange, as well as the Luxembourg-based clearing house Clearstream and the derivatives platform Eurex.

In addition to its previous ambitions to tie the knot with the LSE, Deutsche Boerse also tried to combine forces with NYSE Euronext in 2011, which operated the New York, Paris, Amsterdam, Brussels and Lisbon exchanges at the time.

A joined LSE and Deutsche Boerse would compete with the likes of CME and ICE in the United States and the Hong Kong stock exchange.

LSE chief Rolet said "it would be the largest stock exchange group in the world" by revenue.

The merger would deliver "significant value creation through cost synergies of 450 million euros per year", both sides said.