French Interior Minister Claude Gueant said many of the EU nations back the principle of a Franco-German proposal that includes a reintroduction of national border controls for a month, if a country is faced with a sudden surge of illegal immigration.

Some countries, though, had objections over when and how national controls could be reintroduced. Under current rules, the so-called Schengen zone of 26 European nations protects its common outside borders only, and allows free travel inside the member nations.

The system is flawed where borders are at their weakest, allowing for tens of thousands of illegal immigrants to pour into the Schengen zone every year through the Mediterranean coastline or the Greek-Turkish border.

Unless the fight against illegal immigration is intensified, Gueant said, "a time will come when the European citizens will prefer to question the advantages of the freedom of movement rather than have waves of illegal immigration coming in."

Immigration has vaulted high into the French campaign following the strong performance of far-right, anti-immigration candidate Marine Le Pen in Sunday's first round balloting. Many pollsters say conservative President Nicolas Sarkozy needs to recoup a good chunk of her electorate to stand a chance of winning his tough re-election battle in the May 6 runoff.

"We have some 400,000 people who enter the EU zone illegally each year and between 2 and 4 million clandestine people who live in Europe," Gueant said. "Our citizens, and the European citizens, do not accept illegal immigration."

Together with the common euro currency, which already is under threat because of the financial crisis, the borderless travel principle through much of the EU is seen as one of its greatest palpable achievements.

Last month, Sarkozy said he would pull France out of Schengen in a year, if he is re-elected and if the EU doesn't do more against illegal immigration.

"Sarkozy has given one year. We still have 11 months," Gueant said, confirming the French threat in the margins of a meeting of the 27 EU interior ministers.

Sarkozy has pledged to halve the number of immigrants who enter France each year to 100,000 and limit their state benefits. Le Pen went further, promising to aim for a reduction of 95 percent of incoming immigrants.

Socialist Francois Hollande has pledged to make annual reviews on how many immigrants France should allow in and wants special teams to reduce illegal immigration.

Gueant denied he is seeking to bring the French elections into an EU meeting. "It is always opportune to raise important proposals for our citizens and for the future of Europe."

EU officials said many member states were guarded in their initial response to the Franco-German initiative considering the French election climate.

Last week, Berlin and Paris sent a joint letter to the European Union demanding the "nonnegotiable" right to re-establish national border controls for a month if need be. Many at the time questioned whether it was a move of support of German Chancellor Angela Merkel for her embattled ally Sarkozy.