By Brian Love

PARIS, Sept 6 (Reuters) - France faces serious rail and airtraffic disruption from strikes beginning late on Monday astrade unions seek to mobilise millions of protesters againstplans to raise the retirement age.

The strikes, mostly scheduled to last 24 hours and organisedto coincide with the presentation of a pension reform bill toparliament on Tuesday, are expected to hit public transport andschools badly.

The labour unrest mirrors action in several Europeancountries against austerity measures imposed to reduce budget deficits swollen by the 2008-9 economic crisis. Governments fromGreece to Spain, Italy and Romania have faced down strikers toimpose painful pay and public spending cuts.

London's underground rail network also faces disruption onTuesday as workers strike over pay and job cuts following theworst economic downturn since World War Two.

The French unions, who backed street marches on Saturdayover President Nicolas Sarkozy's law-and-order stance followinga mass expulsion of Roma immigrants, hope two million people ormore will take to the streets for Tuesday's pension protest.

"This is a grave moment," said Bernard Thibault, leader ofthe CGT union, one of the two largest in the country. "This maybe an exceptional day. If it is exceptional, we may be at aturning point."

Didier Le Reste, leader of the CGT rail workers' division,denounced what he called a "brutal" reform, telling Le Parisiennewspaper that 60 percent of train drivers were expected to jointhe strikes.

Sarkozy says he is ready to make some concessions but willnot retreat on the essentials of the reform -- raising theminimum retirement age to 62 from 60, and the age at whichpeople can retire on full pension to 67 from 65.

Sarkozy is caught between a rock and a hard place ahead ofelections in 2012. He needs to leave his mark after promises ofa break with France's failure to embrace economic reform and healso has to slash a swollen deficit, which either means years ofausterity or upward creep in taxation, or both.

DISRUPTION

France's SNCF state railway company said intercity and localtrain services would be reduced by 50 percent or more but thatEurostar links with Britain should run normally, with otherinternational services running close to full capacity.

The strike was due to start at 7 p.m. (1700 GMT) on Mondayon the railways and on Paris's RATP urban transport network,where underground rail services were forecast to drop to abouthalf of normal frequency.

Air France said short- and medium-haul flights would be cutto 50 percent of normal on Tuesday at Orly airport south ofParis, and to 90 percent at Charles de Gaulle airport northeastof the capital, but long-haul services should be unaffected.

France's civil aviation authority said it had asked allairlines to cut Paris flights by 25 percent on Tuesday.

Unions at power utility EdF and oil group Total plan to stopwork at nuclear power stations and refineries but not to anextent that would cause cuts in household energy supplies.

"The ultimate impact of the strike could be power cuts, butwe are responsible," one union official said. All the main unions are urging private sector employees tojoin public sector staff for a one-day stoppage and streetprotests that they hope will match or exceed the two millionpeople they counted nationwide at a similar protest in June.

They will meet on Wednesday to discuss what, if any, furtheraction they take. For more details, click on

GOVERNMENT STANDS FIRM

Frederic Lefebvre, spokesman for Sarkozy's UMP party,repeated the government's determination to proceed with the mainelements of a reform which could go down as the hallmark ofSarkozy's five-year term ending in 2012.

"A reform as crucial as this takes courage and we've gotit," he told France 2 television.

Three in four French people back the protest over a reformwhich two-thirds believe is unfair, a survey showed on Monday.But worryingly for the unions, 65 percent believe the protestwill have no impact, according to the opinion poll conducted byObea-Infraforces poll.

Without major changes such as the rise in retirement age,France's pay-as-you-go pension system would run up annualdeficits of 50 billion euros ($67 billion) by 2020, thegovernment says.

(Additional reporting by Muriel Boselli and Mathilde Cru;Editing by Michael Roddy and Paul Taylor)