Chi-X, the pan-European trading platform owned by a consortium of investment banks including Goldman Sachs and Morgan Stanley, is believed to be close to agreeing to a $360m (£223m) takeover by US rival Bats Global Markets.
The deal, which could be announced within a week, is the latest in a wave of mergers among exchange companies. Deutsche Börse has agreed to buy NYSE Euronext, and the London Stock Exchange has teamed up with its Toronto counterpart.
The creation of new hi-tech platforms such as Chi-X and Bats has revolutionised trading over the past decade, and led to considerable competition between exchanges. The Bats-Chi-X deal would bring together two of Europe's most successful multilateral trading platforms.