The chief executive of Deutsche Börse said his planned merger with the London Stock Exchange Group wouldn’t close before the first quarter of next year because of intense regulatory scrutiny and that US rivals could potentially still torpedo the deal to create Europe’s biggest stock-market operator.

"We don't expect the deal to close before next year's first quarter because regulators have to give their OK following shareholder approval," Carsten Kengeter told journalists in Frankfurt on May 30.