The EU is set to re-commit itself to "our common future" at a summit marking its 60th anniversary, defying Brexit and growing euroscepticism, according to a draft declaration.
They also vow to work for "even greater unity" while allowing "different paces and intensity" of cooperation -- a notion which could fuel tensions among member states.
"We are determined to make the EU stronger and more resilient, through even greater unity and solidarity amongst us," says the draft document by 27 member states and EU institutions, dated March 16.
The declaration is likely to be subject to negotiation by EU nations ahead of a summit on March 25 summit, marking the 60th anniversary of the bloc's founding Treaty of Rome.
The Rome anniversary summit comes at a critical juncture for the European Union, with Britain about to trigger divorce talks while other eurosceptic movements vie for power.
The one-and-a-half page text, a copy of which was obtained by AFP Saturday, vows: "Unity is both a necessity and our free choice.
"Taken individually, we would be sidelined by global dynamics. Standing together is our best chance to influence them, and to defend our common interests and values."
But it continues: "We will act together whenever possible, at different paces and intensity where necessary, as we have done in the past within the treaty framework and leaving the door open to those who want to join later."
The wording evokes the notion of a two-speed or multi-speed Europe, backed by EU heavyweights France and Germany in response to Brexit.
But it is resisted by newer central and eastern European EU members, led by Poland, who fear being left behind.
The draft document, written in English, the bloc's main working language even though Britain is about to leave, may well be subject to change before the Rome summit.
But some parts are more likely to remain as they are.
"Our Union is undivided and indivisible," says the statement, whose final phrase is the same as the declaration which marked the 50th anniversary of the Rome.
"We have united for the better. Europe is our common future," it says.
Adopted by 27 countries a decade ago, that document aimed at relaunching the EU after the crisis triggered by French and Dutch voters' rejection of an EU constitution.
The Rome summit will be clouded by Brexit, but also by upcoming elections in France and Germany where populist forces are vying for power, despite far-righter Geert Wilders' failure to make a breakthrough in Dutch polls last week.