But Francioni did not rule out further involvement in expansion or consolidation of the industry, both at home and abroad.
 
The decision came as seven of Europe's biggest investment banks said they were working on their own stock-trading platform aimed at competing with the London Stock Exchange.
 
Key issues
 
The banks involved include Citigroup, Credit Suisse, Deutsche Bank, Goldman Sachs, Merrill Lynch, Morgan Stanley and UBS.
 
Politicians from most European countries and Jean-Claude Trichet, president of the European Central Bank, have highlighted the advantages of a pan-European exchange, noting that it would serve as a counterbalance to the New York Stock Exchange and Nasdaq in the United States.
 
But Euronext has favoured the New York Stock Exchange over Deutsche Boerse.
 
The New York exchange has forecast that the deal, which needs the approval of shareholders from both sides, will close in the first quarter of 2007.
 
However, it has drawn criticism from some Euronext shareholders who would prefer an all-European deal.
 
Deutsche Boerse said that during the course of talks about signing a letter of intent, an agreement over "certain key issues" arose and could not be overcome. Neither company disclosed the nature of the problem.