Brexit or no, Europe's "realists" to contain "utopians"

* Whatever referendum result, EU faces tough choices on unity

* Federalists say answer is deeper, faster integration

* Critics say that has fuelled UK and other euroscepticism

* Summit next week will see call for rethink, modest ambitions

By Jan Strupczewski and Alastair Macdonald

BRUSSELS, June 23 (Reuters) - Whether Britain stays or leaves the European Union after Thursday's referendum, EU leaders are preparing for a clash over how to respond to popular disillusion with the bloc.

The Brexit debate is echoed in mounting euroscepticism across much of the continent. This is fuelling a struggle which, crudely put, pits those who want a more integrated Union against self-styled "realists", who dismiss them as "utopian" dreamers disregarding democratic attachment to nation states.

Positions are more nuanced and few leaders are arguing for a big shift in power to Brussels.

But the confrontation can be seen in permanent tensions between the central institutions of the European Parliament and the executive European Commission on one hand and a majority of the 28 governments that wield ultimate power in the Council.

Nations' resistance to ceding rights surfaces in fury among some governments at the Commission's drive to force them to take in refugees or to accept more intrusive EU supervision of euro zone budgets. It puts any federalists on the weaker foot -- not least as France and Germany prepare elections next year with eurosceptics riding high in the polls.

Council President Donald Tusk, who will chair a summit on Tuesday and Wednesday to react to the British vote, called on leaders to use the moment to reflect on where Europe has gone wrong. He has also argued that pushing for "more Europe" would only fuel popular hostility to the EU.

"Whatever its result is going to be, we must take a long, hard look on the future of the Union," Tusk said on Monday. "We would be foolish if we ignored such a warning signal."

The former Polish premier has denounced "utopian dreams" of a post-national Europe: "Promoting them only leads to the strengthening of eurosceptic moods," he said earlier this month.

NO "GREAT LEAP FORWARD"

Some in Brussels interpreted his barbs as aimed at Commission President Jean-Claude Juncker, the Luxemburger whose executive enraged some national leaders by pushing them to accept binding quotas of refugees.

EU officials dismiss critics' suggestions that Juncker seeks a "great leap forward" in EU integration after the British vote. Whatever his ideals, he recognises there is no appetite for it among states.

His focus if Britain leaves, the officials said, would be to help keep the other 27 from disintegrating in its wake.