PARIS - President Nicolas Sarkozy was holding firm Sunday on his plan to raise France's retirement age to 62 with the government vowing to squelch efforts to block fuel after strikes fanned fears of a shortage.

Strikers have blockaded a dozen French refineries and numerous oil depots in the last week as part of widespread protests of the government's plan to end the near-sacred right to retire at 60, leading to a run on gas stations by motorists and concerns about fuel shortages at the country's main airport.

"I won't let the French economy suffer from a supply blockage," Prime Minister Francois Fillon said.

"The right to strike isn't the right to stop access to a fuel depot. That's an illegal action," the prime minister said on the TF1 channel.

Fillon spoke hours after unions vowed to do all they could to get Sarkozy to buckle and withdraw his plan or open up negotiations with them in the make-or-break period ahead of a Senate vote Wednesday on the package.

Rail unions called for new transport strikes starting Tuesday to coincide with a sixth round of nationwide demonstrations, ahead of the Senate vote.

The union leaders also called for support strikes from other sectors, including energy, postal workers and private commerce, and for the participation of employees at Eurotunnel, which runs freight and passengers under the English Channel to London. Truckers are expected to join strikes as early as Monday.

Demonstrations Saturday brought at least 825,000 people into the streets, police have said, down from previous protests.

"The head of state and the government are scorning the people," said Didier Le Reste, head of the hardline CGT union's rail branch, accusing the government of being "arrogant" and "deaf" for refusing to negotiate.

The SNCF train authority, already partially hobbled by walkouts, said only half of the fast trains were expected to run Monday, with Paris-London traffic on the Eurostar remaining normal.

The government, meanwhile, tried to assuage fears of a fuel shortage despite dry gas pumps in scattered areas of France and an advisory that short- and medium-haul flights to Paris' Charles de Gaulle airport must arrive with enough fuel to get back home.

"There is no shortage. I won't let them block our country," Fillon said, adding that "we will make the necessary decisions."

French police moved in last week to free up three key refineries.

Transport Minister Dominique Bussereau told Europe-1 radio Sunday that he was not concerned about fuel supplies at Paris' main airport. Strikes had shut down a fuel pipeline but the airport is now "perfectly fed" after fuel began flowing again this weekend, he said.

"There are no worries at Roissy (Charles de Gaulle) and even less at Orly," the minister said, referring to the smaller airport south of Paris which reportedly has fuel stocks for up to 17 days.

Labour Minister Eric Woerth reiterated that "there is no risk of a shortage" of fuel for planes or cars even if there are occasional problems at the pump as motorists compete to fill up.

Woerth denied union claims that the government is provoking unions with its refusal to negotiate.

"We're not looking for a confrontation," he said in a TV interview on the iTele channel.

Sarkozy has remained uncharacteristically silent on the contentious issue, allowing government members to speak in his place. With his popularity sinking ahead of 2012 elections, the once ever-present leader who personally received union representatives at the Elysee Palace has made himself less visible in a likely bid to capture the presidential aura of distant authority familiar to the French.

But presidential demeanour and government assurances that working longer will help the children of France has so far failed to win over protesters.

"I think there are things happening in France at the moment which should draw everyone into the streets," said Laurence Romeyer, a 44-year-old teacher in Lyon, reflecting the opinion of many protesters. "I agree with the people who are on strike, so whether I have gas or not is a minor issue," she told Associated Press Television News.

One motorist from a village near Fontainbleu said she drove 30 miles (50 kilometres) all the way to Paris in order to buy fuel.

"It's better to buy, because at home, the filling stations are closed. It's a bit of a shock for us," said Emilia Scoubel, a 30-year-old office worker.

Countries across Europe are cutting spending and raising taxes to bring down record deficits and debts from the worst recession in 70 years. Labor leaders, students and civil servants are fighting back.

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