European Union (EU) flags fly in front of the European Central Bank (ECB) headquarters in Frankfurt, Germany, December 3, 2015. [Photo/Agencies]

NAPLES, Italy - The leaders of Germany, France and Italy will meet on Monday to discuss how to keep the European project together in the second set of talks between the premiers of the euro zone's three largest economies since Britain's shock vote to leave the bloc.

Italian Prime Minister Matteo Renzi hosts German Chancellor Angela Merkel and French President Francois Hollande on an island off the coast of Naples ahead of September's EU summit called to discuss reverberations from the Brexit vote.

Officials in Brussels and Berlin fear the June 23 vote could lead to a referendum in the Netherlands - a founding member of the union - on whether to also leave the bloc.

"Monday aims to show the unity of Europe's three biggest countries, but not to create a specific club," a French diplomatic source said, noting that the aim was to prepare for the groundwork for the forthcoming Bratislava summit.

Faced with existential risks, Merkel wants to cement "a better Europe" rather than forge ahead with "more Europe". Renzi wants Italy to have a strong voice in how the bloc's future is shaped after Brexit and, according to the French diplomatic source, Hollande wants an EU-wide investment plan to be doubled.

The three leaders differ over how to boost economic growth - which slowed across the 28-nation bloc in the second quarter and stagnated in France and Italy - and cut unemployment.

France supports Renzi's push for expansionary measures and against austerity, Germany is likely to oppose any undermining of Europe's deficit and the debt constraints that Italy and France have struggled to comply with.

Italy is eager for greater European consolidation in the wake of Brexit, but Merkel is more concerned about preserving the integrity of the eventual 27-member bloc.

For her it will be the beginning of a whirlwind week of meetings with other European governments that will see her travel to four countries and receive leaders from another eight.

"The goal must first of all be to preserve the status quo and to prevent a further disintegration of the EU-27," said one EU diplomat.

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Renzi chose to meet on the island of Ventotene because of its symbolic significance as the place where two Italian intellectuals, held there in World War Two, wrote an influential manifesto calling for European political unification.

One of the two, Altiero Spinelli, is buried on the island and the three leaders will lay a wreath on his tomb.

Lingering threats to the union that emerged long before the Brexit vote are also likely to be on the agenda, including internal and external security after Islamist militant attacks and Europe's migration crisis.

Emboldened by the Brexit vote, Hungary's Prime Minister Viktor Orban has called a referendum on Oct. 2 on whether to accept any future EU migrant settlement quotas as his government steps up its fight against the EU's migration policies.

In another symbolic choice of venue, the three leaders will hold their closing news conference on the Italian aircraft carrier, the Garibaldi, which is the flagship of the EU's "Sophia" mission in the Mediterranean.

The naval operation has a mandate to tackle migrant smugglers, help enforce an arms embargo off Libya, and train the Libyan coast guard.

The EU plans to offer incentives to African governments to help slow the flow of migrants who have poured into Europe over the past three years, but disagreements on how to handle the situation have laid bare divisions between member states.

Italy, the main entry point for Africans but rarely their planned destination, is struggling to house migrants turned back from neighbouring countries including France, and has disagreed with Germany over how to finance the response.