French rail workers have rejected a new offer of talks by employers, voting to extend their action against President Nicolas Sarkozy's pension reforms.
Transport services in the capital will be severely disrupted on Sunday
The country's largest rail union said the offer by state rail firm SNCF "did not respond to all the issues".
Crippling transport strikes were therefore set to extend to a fifth day.
Prime Minister Francois Fillon said that unions must first return to work before any negotiations could begin on the rail workers' privileged pensions.
"We demand, for negotiations to resume, that there is a call by the unions to return to work," he told a press conference on Saturday.
"It is not possible to strike and negotiate at the same time," he said.
President Sarkozy, Mr Fillon and Labour Minister Xavier Bertrand held another round of talks on Saturday evening, officials said.
The proposals by SNCF suggested month-long talks should start on Wednesday.
The country's fourth largest railway union has recommended suspending action, as it says the strike is losing support, but all other unions are in favour of the stoppages.
Meanwhile, the SNCF warned that transport services would remain severely disrupted on Sunday, with only 250 of the country's 700 high-speed TGV trains operating.
It said Paris metro lines would see one train in five run, and that bus and tram services would be cut to 40%.
The industrial action is costing the French economy 400m euros ($590m; £295m) a day, French newspaper Le Figaro reported.
The strike, which began on Tuesday night, was triggered by plans to scrap "special" pensions privileges enjoyed by 500,000 workers, mainly in the rail and energy sectors, as well as 1.1 million pensioners.
The French government last tried to overhaul "special" pensions in 1995. The move sparked three weeks of strikes that forced then-President Jacques Chirac to climb down.
But the polls have so far broadly supported Mr Sarkozy, who says France can no longer afford to let some public sector employees retire on a full pension as early as 50.
The deadlock over the transport systems comes ahead of planned - but separate - strikes by civil servants, lawyers and magistrates on Tuesday.