Germany's stock market Deutsche Bourse plans to merge with its Swiss rival, sources familiar with the situation told Reuters on Sunday.
"The aim of the invitation by the Deutsche Bourse to its Swiss partner is a merger," said one source.
The Swiss exchange operator, SWX, said it had been invited to discussions but it had yet to decide whether to pursue the talks with the Germans.
SWX, which already co-owns the successful Eurex futures and options exchange with Deutsche Bourse, also said both parties had agreed not to comment on the content of the letter of invitation.
The German and Swiss exchanges already have close links, forged by the launch in 1998 of the world's biggest derivative trading platform. The German operator has made no secret of its desire to expand.
The Frankfurt-based exchange has focused its attention on the London Stock Exchange despite failing to clinch a tie-up in 2000.
Further consolidation in the stock exchange industry is seen as inevitable by many analysts as a single European market in financial services emerges.