French President Nicolas Sarkozy has threatened to withdraw from Europe's open border zone unless more is done to stop illegal immigration.

法国总统萨科奇警告道，如果欧盟不解决非法移民问题，法国将退出边境免税贸易区。

Speaking at a Paris campaign rally, the president said that reform was the only way to avoid the "implosion¹" of Europe.

He said that unless there is progress in the next 12 months, then France would suspend participation² in the Schengen agreement.

The accord allows passport-free travel among 25 European nations.

Illegal immigration has been a key issue ahead of the presidential election.

Last week Mr Sarkozy said there were too many foreigners in France - and pledged to halve³ the number of immigrants arriving if he is re-elected later this year.

The first round of voting is on 22 April. He is lagging in the opinion polls far behind the Socialist⁴ candidate, Francois Hollande.

The European Commission is due to submit a report on the operation of the Schengen system in May.

Mr Sarkozy also called for a "Buy European Act" that would require governments to favour European-made products.

He said: "France will ask Europe to 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.''