President Jacques Chirac of France is due to inaugurate the latest addition to the country's vaunted high-speed rail - or TGV - network on Thursday.

The new track extension will link Paris to the Mediterranean coast at Marseille in just three hours.

Politicians and businessmen in the south hope it will be a major boost to the region's economic development.

The new 250km (155 miles) addition to the long-established Paris-to-Lyon service has been 10 years in the building and cost FF25bn (US3bn).

Environmental concerns

A large part of the money went on overcoming a succession of environmental objections, such as a detour to avoid a pair of protected eagles.

It sweeps down the east bank of the River Rhone, the corridor since ancient times connecting the Mediterranean with the French interior, and its completion means the country's three biggest cities are now linked in the TGV system.

Three hours from Paris to Marseille slices one hour and 20 minutes off the existing travel time and should result in a major switch from air to rail and a big increase in tourism from the north.

Milestone

In Marseille, they are hoping the TGV will also help the city's regeneration from seedy, post-colonial dockyard to high-tech Mediterranean business centre.

And in the longer term, the opening of the line could be seen as a symbolic milestone in a process already under way, which consists in a gradual demographic shift towards the south.