The London Stock Exchange is moving to merge with its counterpart the TMX in Toronto, Canada.
That would create a top centre for trading in mining and energy shares provided that political opposition in Canada can be overcome.
The value of trading particularly in mining has surged in recent years as demand from fast-growing emerging economies drives a boom in commodity prices.
It is an all share deal with Toronto stockholders receiving almost three LSE shares for each of theirs. The two exchanges together would trade 6,700 companies.
However, the Canadian government may move to block the TMX deal, as it did with a hostile takeover bid for Potash Corporation by BHP Billiton. It can reject larger takeovers by foreign companies if they do not provide a “net benefit” to Canada.
At the same time Germany’s Deutsche Boerse and NYSE Euronext confirmed they are talking but said it was still not certain that they would merge.
Trading in Deutsche Boerse shares was halted on Wednesday after speculation of a potential merger deal between the two was pending.