The summit marked 60 years since the founding of the European Economic Community. We will act together, at different paces and intensity where necessary, while moving in the same direction, as we have done in the past, in line with the Treaties and keeping the door open to those who want to join later. "Some people will deem it to be overambitious, some will deem it to be not ambitious enough", Gentiloni added.
With the EU facing crises including migration, a moribund economy, terrorism and populism, as well as Brexit, EU President Donald Tusk called for leadership to shore up the bloc.
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"Today, we celebrate the perseverance and the cleverness of EU's founding fathers, which has its best proof in this crowded hall", Gentiloni said in his opening speech in the very place where the Treaty of Rome was signed 60 years ago.
"The return to Rome must not simply be a remembrance of things of the past, " said the pontiff, an outspoken supporter of the EU.
He said: "Prove today that you are the leaders of Europe, that you can care for this great legacy we inherited from the heroes of European integration 60 years ago".
Others in Italy, such as Senator Michela Montevecchi of Five Star anti-establishment movement - now leading in the polls with more than 30 per cent support among Italians - are less invested in whether the European Union survives.
The divisions in the European Union have deepened considerably since the 2008 financial crisis and the subsequent deep recession that sent unemployment into double digit levels and triggered the bailouts of Greece, Ireland and Portugal and the rescue of Spain's banks.
A safe and secure Europe: a Union where all citizens feel safe and can move freely, where our external borders are secured, with an efficient, responsible and sustainable migration policy, respecting worldwide norms; a Europe determined to fight terrorism and organised crime.
Then, one by one, the 27 leaders, signed the Declaration of Rome. We have united for the better.
It pledges that the European Union will listen better to the citizens, deliver results more efficiently, work more closely with national parliaments.
All leaders ran through the EU's long history, looking forward to a safer, more prosperous, social Europe, with a stronger position in the global scene.
Two marches have been authorised on Friday, with 6,500 pro-EU demonstrators expected in the morning and 13,000 anti-EU protesters in the afternoon.
Long the mantra of the EU, the "ever closer union" pointed toward a seamless continent and an economic and political juggernaut.
Francis told the 27 leaders that while the European Union founders were "inspired by the hope of a better future ... our time is dominated more by the concept of crisis".
At the end of the session, all 27 leaders signed the Rome Declaration saying that "European unity is a bold, farsighted endeavor".
Previous objections from Poland and Greece on the blueprint - about the idea of a multi-speed Europe and EU's austerity policies, respectively - were lifted ahead of the ceremony.
Britain says that it will trigger the negotiations to leave the bloc on March 29, only days after the summit.