Italy and Germany's stock exchanges have agreed to work on proposals for a three-way merger which would include pan-European exchange Euronext.
Supporters would like to see a federal European stock exchange
Borsa Italiana said it and Deutsche Boerse hoped to form a federal European exchange "that includes Euronext".
The plan follows the current $10bn (£5.4bn; 8bn euro) takeover offer for Euronext by NYSE Group, which operates the New York Stock Exchange.
Euronext runs exchanges in Paris, Lisbon, Belgium and Amsterdam.
A Euronext spokesman said: "We signed a combination agreement with New York Stock Exchange in June, and we are working on that merger.
"We have since invited the cash businesses of Deutsche Borse and Borsa Italiana to join the new global exchange in parallel with that deal."
The Milan-based Borsa Italiana said its board had approved the signing of a letter of intent with Deutsche Boerse.
The German exchange has been keen to develop closer ties with Euronext since its plans to take over the London Stock Exchange acrimoniously fell apart last year.
"(The) letter of intent ... (would aim) at creating a federal European exchange that includes Euronext," Borsa Italiana said in a brief statement on Thursday.
Italian board member Massimo Segre said the letter aimed to provide "an alternative and better proposal than the one by NYSE for Euronext".
The idea of a federal European exchange has already won the backing of French President Jacques Chirac, who has said he would like to see a "European solution" to the question of Euronext's future.