Euronext has agreed to buy Paris-based LCH SA for 510 million euros (433 million pounds), but the deal can only go ahead if LSE Group succeeds in merging with Deutsche Boerse (DB1Gn.DE), a tie-up regulators will rule on by the end of June.
"If the merger ... is not completed for whatever reason, we will pursue alternatives to offer the best clearing services to our clients," Euronext Chairman and CEO Stephane Boujnah said on Wednesday after reporting stable full-year earnings.
A clearing house ensures a stock, bond and derivatives trade is completed even if one side of the transaction goes bust.
LCH SA is authorised to clear derivatives, an activity that is set to grow sharply, and Euronext's contract expires in 2018.
Euronext, which operates bourses in Paris, Amsterdam, Brussels, London and Lisbon, would be dwarfed by an Deutsche-Boerse-LSE tie-up and has opposed the combination.
Asked if he still opposed the merger, Boujnah said that "whatever has to be said has been said", and it was now a question of getting the best for Euronext shareholders.
Euronext said its full-year core earnings were stable, as reduced costs offset a drop in listing and trading volumes following Britain's vote to leave the European Union.
Total capital raised in primary activity fell to 3.73 billion euros ($3.95 billion) from 28 new listings, against 12.40 billion euros a year earlier from 52 listings, it said.
Trading activity for the year was "marked by lower volumes" due to uncertainty after the Brexit vote and lower volatility.
Euronext said it would launch a pan-European platform in mid-2017 aimed at shielding trading of blocks of shares from so-called high frequency traders, who have been criticised by other market participants as having an unfair speed advantage.
Rivals like the LSE have already set up similar platforms ahead of new EU rules in January 2018 that allow asset managers to trade blocks of shares off the public market.
Euronext also announced a new electronic platform called Chequers to help customers back their commodity, bond and stock trades with collateral in case of default.
It also plans to become a content provider of reference on agricultural products and other commodity markets by seeking a "suitable acquisition target".
Euronext said earnings before interest, tax, depreciation and amortisation (EBITDA) were stable at 283.9 million euros for 2016, slightly ahead of analysts' expectations.
Operating expenses for the year fell 9.4 percent to 212.5 million euros from 234.7 million euros a year earlier. The company's EBITDA margin rose to 57.2 percent, up from 54.7 percent a year ago.
Editing by Gopakumar Warrier/Sunil Nair/Alexander Smith