The announcement comes amid warnings that the continuation of rail strikes could affect factory output.
"In the absence of [freight] trains, factories, notably in the chemical and car manufacturing sectors, are going to be unable to work," Guillaume Pepy, an executive with SNCF, a state-owned rail company, told Le Parisien newspaper.
Shop and restaurant owners in Paris, the capital, have complained that the rail strike has cost them business, although analysts say the macro-economic impact of the strike has so far been limited.
The railway unions, which are protesting against planned pension reforms, are due to announce their next step on Sunday.
Opinion polls have showed the rail strike is unpopular with most French voters, but the French government, struggling to meet growth goals, knows it cannot afford to let the protest drag on or risk a wider social conflict.
Another poll from the Le Journal du Dimanche newspaper found political support for Nicolas Sarkozy, the president, has declined to 55 per cent, a drop of four points in the month and his lowest score since his election in May.
Union leaders are also in a dilemma as their members have so far signalled little willingness to negotiate.
"It's a strike that not many really wanted and, therefore, no one really knows how to get out of," Le Journal du Dimanche said in an editorial.
The rail unions oppose plans to scrap special pension privileges that allow some 500,000 public sector workers to retire on full pensions after paying contributions for 37.5 years, instead of 40 years for other workers.