France's incumbent president and Union for a Popular Movement candidate for 2012 presidential election Nicolas Sarkozy delivers a speech during a campaign meeting on Sunday in Villepinte, outside of Paris. (THOMAS COEX/AFP/GETTY IMAGES)

President Nicolas Sarkozy, running from behind for reelection, pledged Sunday to pull France out of Europe’s 25-nation visa-free zone unless border controls are tightened to prevent illegal immigrants from sneaking in to find jobs.

The pledge, at a boisterous rally with 80,000 supporters in a Paris suburb, marked the latest in a series of campaign promises designed to appeal to conservative and nationalistic French voters by choking off long-controversial legal and illegal immigration into France.

It was part of a no-holds-barred effort by Sarkozy to raise his standing with voters before the two-round ballot scheduled for April 22 and May 6. The president, finishing a first five-year term, has been running steadily behind his main adversary, Francois Hollande of the Socialist Party, in months of polling, leading his followers to worry out loud that he could lose.

In the pressure cooker of the campaign, immigration repeatedly has flared as an emotional issue in a country already uncomfortable with more than 5 million Muslims — many are French citizens, others fresh arrivals — who live here legally or under the radar and are increasingly visible in a society deeply rooted in Christian tradition.

The latest flareup involved halal meat, or meat prepared according to Islamic tradition. The far-right National Front candidate, Marine Le Pen, attracted attention by saying it was being widely sold to unknowing French families. Sarkozy at first dismissed the claim as frivolous. But then, sensing an opening to gain right-wing votes, he demanded that all meat be labeled with the method according to which the animal was slaughtered.

French President Nicolas Sarkozy holds a huge rally Sunday in hopes of energizing his campaign as polls show him lagging behind Socialist rival. (THOMAS COEX/AFP/GETTY IMAGES)

In the same vein, Sarkozy promised last week to cut by half the number of immigrants allowed into the country under rules designed to bring families together. The Interior Ministry, headed by a close Sarkozy lieutenant, Claude Gueant, reported in January that 12,613 residence permits were granted in 2011 for family reunification, down 14 percent from the previous year.

Europe’s visa-free area, called the Schengen zone after the Luxembourg city where it was negotiated in 1985, was considered a major stepping stone to European unity . It comprises all 27 European Union countries except Britain and Ireland.

According to the Schengen rules, anyone who enters a European country can move into other European countries without a separate visa. The freedom of movement has been a boon for thousands of illegal immigrants from strife-torn North African and Middle Eastern countries, who often enter Greece from Turkey and move on to Germany, France or Italy to seek black market jobs without being stopped at borders.

To reduce the flow, the European Union deployed a new pan-European police force along the 160-mile Greece-Turkey border two years ago. At that time, as many as 350 illegal immigrants a day were being taken into custody along the porous border.

But the flow has continued. Seven governments in the Schengen area called last week for a new plan to stem the tide. Sarkozy, going a step further, said the whole accord might have to be renegotiated if a solution is not found.

“If I note within the next 12 months that no serious progress has been made in this direction, France will suspend its participation in the Schengen accords until the negotiations are completed,” he said. “There is no question of our submitting to the insufficiencies of European border controls.”