French truckers moved a step closer to staging crippling blockades across the country after pay talks with employers broke down on Friday night.

Union leaders have threatened to jam motorways, oil depots and other key sites from Sunday night unless their demands for higher salaries and an extra month's pay are met.

The current state of discussions is not of a nature to resolve the crisis

Alain Arquier, CGT union

French Prime Minister Jean-Pierre Raffarin has warned he will not permit the truckers to paralyse the country like they did in 1996 and 1997.

The threat of action came as several thousand French farmers blockaded the exits of food warehouses for a second day, demanding a better deal from supermarkets.

The supermarkets' association says shops will start running short of fresh fruit and vegetables in two days.

The farmers say the stores are raising prices while paying farmers less and less.

Meanwhile, thousands of French motorists have been queuing up at petrol stations to stock up with reserves of fuel amid fears the refineries will be blockaded by the truckers.

Pay row

Talks between the truckers and hauliers are due to resume on Saturday, but union leaders have expressed scepticism that a last-minute deal can be reached.

"The current state of discussions is not of a nature to resolve the crisis," said Alain Arquier from the CGT union.

The unions are demanding an extra monthly salary - a common practice in France - and a 10% reduction in working hours.

Haulers say they cannot meet the demands because their profits have been marginalised by growing competition in Europe.

Christmas threat

The unions have set a deadline of 2200 local time (2100 GMT) on Sunday night for an agreement to be reached.

Thousands of motorists have stocked up with extra fuel

If talks fail, truckers say they will initially slow traffic down, then blockade fuel depots and other economic targets if negotiations continue to lead nowhere.

Correspondents say a strike in France could severely disrupt European trade routes in the run-up to Christmas.

The French Government is planning to try to keep routes open, deploying riot police near the key river port of Gennevilliers, north of Paris, and placing troops on alert, news agencies reported.

The country's largest oil refiner, TotalFinaElf, says it is keeping stocks at depots and petrol stations topped up to maximum levels, while in Toulouse authorities have reportedly banned motorists from buying extra fuel.