President Nicolas Sarkozy has threatened to pull France out of the European Union's  Schengen zone unless the bloc makes progress on protecting EU borders from illegal immigration.

Mr Sarkozy's pledge on the hot-button theme of immigration came in a wide-ranging speech to thousands of supporters at a boisterous campaign rally, as polls show he faces a tough battle for re-election in April and May.

Unchecked immigration would thwart Europe's ability to take in and integrate new entrants, putting strains on social safety nets for the most disadvantaged across the continent, Mr Sarkozy said to chants of "We're going to win!" against a sea of blue, white and red French flags.

"It's urgent because we cannot accept being subjected to the shortcomings of Europe's external borders," Mr Sarkozy said, calling reform the "only way to avoid the implosion of Europe".

"But if I note within the next 12 months that no serious progress has been made in this direction, then France will suspend its participation in the Schengen accords until these negotiations are completed," he said.

The conservative president also pitched an effort to support purchases of European products within the continent, noting American government laws to support small businesses and domestic industries

"Why is it that Europe should forbid itself from what the United States, the world's most free-market country, allows itself?" Mr Sarkozy said.

"France will ask Europe adopt a Buy European Act on a model of the Buy American Act. That way companies that produce in Europe will benefit from European state money."

Mr Sarkozy trumpeted his role in crafting a bailout fund called the European Stability Mechanism, for debt-laden EU countries like Greece that jolted financial markets and raised doubts about the euro.

He accused Socialist frontrunner Francois Hollande of playing politics with his call for a re-negotiation of that plan. Mr Hollande says it relies too much on austerity and does not do enough to revive growth.

Mr Hollande's campaign chief, Pierre Moscovici, fired back.

"Conservative leaders, who have been so quick to unite to defend the president, will appreciate his threat to pull unilaterally out of the Schengen zone at the same time that he calls for the signature of the austerity treaty in the name of European cohesion," Mr Moscovici said, an apparent reference to endorsements that Sarkozy has received from German chancellor Angela Merkel and other European conservatives.

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