Nicolas Sarkozy remained defiant over his plan to raise France's retirement age to 62 and his government vowed to defeat efforts to block fuel after strikes sparked 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 petrol stations 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."
Mr Fillon spoke hours after unions vowed to do all they could to get President Sarkozy to buckle and withdraw his plan or open up negotiations with them in the make-or-break period before a Senate vote on the package on Wednesday.
Rail unions called for new transport strikes starting tomorrow to coincide with a sixth round of nationwide demonstrations.
The union leaders also called for sympathy strikes from other sectors, including energy, postal workers and private commerce, and for the participation of employees at Eurotunnel. Lorry drivers were expected to join strikes as early as today.
Demonstrations on Saturday brought at least 825,000 people on to the streets, police 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 hit by walkouts, said only half of the fast trains were expected to run today, with Paris-London traffic on the Eurostar remaining normal.
The government, meanwhile, tried to calm fears of a fuel shortage despite dry 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.
French police moved in last week to free up three key refineries.
Transport minister Dominique Bussereau told Europe-1 radio that he was not concerned about fuel supplies at Paris' main airport. Strikes had shut down a fuel pipeline but the airport was 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 denied union claims that the government was provoking unions with its refusal to negotiate.
"We're not looking for a confrontation," he said.
Mr Sarkozy has remained uncharacteristically silent on the contentious issue, allowing government members to speak in his place.
With his popularity sinking before 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.
"I agree with the people who are on strike, so whether I have petrol or not is a minor issue."Reuse content