Bernard Thibault, head of the CGT workers' confederation, made the statement as union leaders prepared to discuss plans to hold a seventh day of national protests across France.

Rubbish has been piling up on the streets of Marseille after nine days of strikes by collectors.

Meanwhile rolling strikes are continuing against government plans to raise the pension age from 60 to 62.

Blockades of refineries and fuel depots have led to fuel shortages.

President Sarkozy has called for an end to the disruption. "This disorder which is aimed at paralysing the country could have consequences for jobs by damaging the normal running of economic activity," he said on Wednesday.

Stepping up action.

Mr Thibault told RMC radio on Thursday: "The government remains intransigent. We need to continue with massive action as soon as next week... We will ask the unions for strong action that will allow people to stop work and go on to the streets."

In the southern port-city of Marseille, there is no public transport, trains have been delayed or cancelled and the ports blockaded, and the nine-day rubbish collectors' strike means several thousand tonnes of refuse is piling up on the city's streets.

The top central government official in the area, Michel Sappin, said: "There is a real danger to the safety and health of Marseille."

The unions' tactics are clear, says the BBC's Matthew Price in the southern port city - to cause discomfort, if not chaos, and to create uncertainty across the country.

They believe that keeps the pressure on the government to change its retirement plans but, adds our correspondent, it also risks alienating the public, who so far according to surveys still support the strikers.

The Senate is due later this week to vote on the pension reforms - aimed at raising the retirement age from 60 to 62 and the full state pension age from 65 to 67.

The lower house has already approved the bill.

Electricity imports.

Ahead of the vote, correspondents say unions are stepping up the pressure on a 10th day of refinery strikes, go-slows on motorways and work stoppages at regional airports.

The BBC's Christian Fraser in Paris says there is a precedent for such a move.

In 2006, student protests forced the government to retreat on the controversial youth labour scheme, even after then President Jacques Chirac had signed it into law.

Some unions want to continue the protests whatever happens in parliament but that will depend on public support and the resolve of their members, many of whom have gone without pay for days even weeks, our correspondent adds.

About a quarter of France's service stations had no fuel on Wednesday, and strikes also stopped work at two of France's three liquefied natural gas (LNG) terminals.

On Wednesday, the country began importing electricity as the wave of protest action took hold of energy supplies.

At least 12 of France's 58 reactors were shut for maintenance but the unions say production has been cut at four others.

As well as the general strikes and protests, there have been six days of co-ordinated action in the past six weeks that have brought as many as three million people to the streets.

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