Martin Schulz told Die Welt's Tuesday edition that the EU was in danger and that there were forces trying to pull it apart.
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He was responding to a recent warning from Jean Asselborn, Luxembourg's foreign affairs and migration minister, that the EU might break apart,
"No one can say whether the EU will still exist in this form in 10 years' time. If we want that then we need to fight very hard for it," Schulz said.
He was not specific about what was threatening the EU, but much of the interview was focussed on the migrant crisis, which has stretched Europe's unity and tolerance during the year.
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Schulz said that the EU was not without alternatives and "could of course be reversed", adding that other options including a Europe in which nationalism, borders and walls were prevalent.
"That would be disastrous because that kind of Europe has repeatedly led our continent into catastrophe," he added.
Divisions in the EU over the migrant crisis are rife, notably between German Chancellor Angela Merkel, who has led efforts to take in more Syrians, and leaders in the formerly Communist East who oppose EU schemes to make them take in some asylum seekers.
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And Europe's passport-free Schengen zone looks under threat too, with some countries re-introducing border controls. Last Thursday Greece asked for European help to secure its borders and care for crowds of migrants, defusing threats from EU allies to bar it from Schengen if it failed to get control.
Schulz said no country could single-handedly tackle challenges like migration, adding that this was only possible together as the EU.
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