Uniting the northern and southern shores of the Mediterranean has been a dream of empire builders since the Romans. Yet proposals to marry the rich nations of the north with the struggling economies of the Arab south have rarely gone beyond grandiose declarations of intent: the economies, histories and cultures of the littoral nations are too diverse to be joined by one sea.

The European Union has tried, nevertheless. Thirteen years ago it launched the Barcelona Process, to boost investment, political dialogue and mutual engagement. The results have been meagre. Yesterday President Sarkozy called heads of state and government from all 27 EU members to meet those southern counterparts willing to attend a weekend conference in Paris to create a new Euro-Mediterranean partnership (see page 31). The outcome may prove a damp squib.

There is nothing wrong with the idea. Many of Europe's problems can be traced to the southern shore of the Mediterranean: illegal immigration, Islamist extremism, terrorism and drug smuggling. The poverty of North African societies ought to prompt huge efforts to even up the balance, with west Europeans investing in the south to take advantage of lower wages, and Arab North Africa exporting to the rich markets of the north. The rapid advance of Eastern Europe sets the example. But such a process has barely begun. The ten southern nations have an average income of only $2,600 per head. Unemployment hovers at about 30 per cent. Trade among the North Africans is minimal, hampered by tariffs. And EU capital investment, which amounted to €8.7 billion between 1995 and 2006, goes disproportionately to a few big countries, such as Egypt.

Mr Sarkozy's “great dream of peace” has been poorly conceived and badly presented. Originally, he invited only EU states bordering the Mediterranean, while calling on all 27 EU members to provide funds. A furious Germany lobbied, with other northern nations, to have a say in how its money was spent. France was then forced to drop plans for a Mediterranean investment bank and proposals for regular EU-style ministerial meetings. Turkey feared that the process would be used to stall its EU accession talks. And amid suspicions that the project was an eye-catching EU presidency initiative to promote French interests and prestige, Paris agreed finally to incorporate the plan into the Barcelona process.

Beyond the high-sounding declarations, however, there will be useful measures: cleaning up sea waters, working on land and maritime “highways”, developing solar energy and student exchanges and setting up a body to help medium and small-sized companies with technical assistance. The meeting has been used to bring Syria in from the cold. President Assad has been given a chance to break away from Iran's suffocating embrace and, on sufferance, has been accepted again as a negotiating partner by the West.

The Paris meeting allowed meetings between Syrians and Lebanese on the sidelines and although the mooted summit with Ehud Olmert, the Israeli Prime Minister, was never likely, the two sides say they have advanced their tentative peace talks. Whether a lasting secretariat and institutions come from the conference remains open. But at least long-separated neighours have been brought closer together.