Leaders of 43 countries from the Middle East, North Africa and Europe are gathering in Paris to launch a new Union for the Mediterranean.
French President Nicolas Sarkozy is hosting the leaders, to discuss issues including regional unrest, immigration and pollution.
Mr Sarkozy announced on Saturday that Syria and Lebanon had agreed to set up embassies in each other's capitals.
Lebanon and Syria have not had fully-fledged embassies in each other's countries since both gained independence from colonial rule in the 1940s.
Relations between the two have been strained since Lebanon's former Prime Minister Rafik Hariri was assassinated in 2005 - an attack which Lebanon claims Syria was involved in.
French Foreign Minister Bernard Kouchner said it was time the region put years of strife behind it and forge new ties with European Union states on the pressing issues of the day.
Mr Kouchner said that there was a "wind of hope" in the Middle East.
But he added: "I regret to say discussions between Israelis and Palestinians are not part of it so far."
Critics have dismissed the new union as lacking substance, and diplomats say there continues to be disagreements over key issues such as how to address the Middle East peace process and a possible role for the Arab League.