French unions launched a major strike Tuesday over President Nicolas Sarkozy's plans to raise the retirement age from 60 to 62, with walkouts causing headaches for travellers and commuters.

More than 200 street demonstrations were scheduled throughout France during the one-day strike. Civil aviation authorities asked airlines to cut a quarter of flights at Paris airports. Only two out of five fast trains are scheduled to run, and traffic was slowed on the French capital's subway and suburban transport lines.

The strike coincides with the start of debate in parliament over a plan to overhaul the money-losing pension system so it will break even in 2018. The government insists the reform is essential as people live longer, and it has urged people to show "courage" as it tries to chip away at the huge national debt.

Unions say the government is attacking one of France's most cherished social protections — though a retirement age of 62 would still be among the lowest in Europe. Neighbouring Germany, for example, has decided to bump up the retirement age from 65 to 67.

Unions hope to mobilize two million street demonstrators at a time when Sarkozy's approval ratings hover in the mid-30-per-cent range. A similar effort June 24 drew nearly 800,000 people.

Labour Minister Eric Woerth has said the government will press ahead with the reform no matter how strong the protest turnout is. Leftist political parties, as well as student associations, have urged members to join in.

The SNCF rail network says travellers can expect 40 per cent of TGV fast trains to run, and 80 per cent of Thalys trains to Belgium and the Netherlands will not be affected. Eurostar trains to Britain are expected to run normally.

Traffic will vary on the Paris subway, with only one out of two or one out of three trains operating on many lines, the RATP transport authority said. Three buses out of four are expected to circulate.

Some suburban trains will be hard-hit. For example, there will be almost no traffic on the line that air travellers take to and from the city.