(Updates with air dispute; petrol rationing; truckers in Marseille, Valance, Genevilliers)
By Brian Love
PARIS, Nov 25 (Reuters) - Truck drivers set up roadblocks across France on Monday in a pay feud, while airlines scrapped dozens of flights due to a walkout by air traffic controllers and tens of thousands of public sector workers prepared for protest marches.
The industrial action by truckers, who mounted almost 40 blockades across the country, started to bite soon after they initiated their stoppage with the lower Normandy region introducing petrol rationing.
Truckers, angry about a pay offer from employers that split the trade union movement, were being closely watched by police who were under orders not to let them paralyse the economy.
"The right to strike must not be confused with blockading the country," Transport Minister Gilles de Robien said.
The truckers' protest was set to snowball with a 32-hour strike by air traffic controllers from Monday evening and marches on Tuesday by tens of thousands of rail workers and other state employees fearful of privatisation and the future of French public services.
British Airways said it had cancelled 64 flights between London and France on Monday and Tuesday. Air France said it would cut a large number of domestic and European flights on Tuesday. French aviation authorities said wider disruption was expected.
FOOD DEPOTS TARGETED
Roadblocks began Sunday night. Protesters tried to step up the pace on Monday, setting up roadblocks at key food depots in Lille in the north and Toulouse in the southwest.
One blockade outside the airport in the southern city of Marseille was abandoned before midday. Union officials said the blockage had ended due to "police pressure".
A blockade near Valence in southern France ended when police took several union representatives away for questioning, but another blockage set up nearby rapidly, witnesses said.
Media said union divisions seemed to have hurt the protest, but the number of blockades rose as the day wore on and truckers appeared to be playing "cat and mouse" by moving blockades from one spot to another to avoid police confiscating licences.
Two trade unions that represent a large majority of truck drivers, the CFDT and CGT, faced a serious test of fire power on the first full day of protest, after several small unions broke ranks to agree a pay deal with employers on Sunday evening.
Protesters, mostly summoned by the CFDT and CGT unions, used lorries and cars to block the Lille food depot.
Truck drivers set up a roadblock on the ringroad around the city of Caen, west of Paris, letting private motorists pass but stopping trucks. Similar blockades were under way near the Channel shipping port of Le Havre and another one on a key entry point to the motorway from the north to Paris.
That was still well short of the hundreds of blockades that dried up petrol stations and choked food supplies, borders and international freight in conflicts in 1992, 1996 and 1997.
"We're a long way from nationwide blockade even if things are far from perfect this morning," said junior transport minister Dominique Busereau, appealing to truckers to get back to negotiations with employers.
Bernard Thibault, national leader of the CGT union, played down the union divisions. "We will need a few more hours to evaluate the situation," he said.
STANDOFF WITH GOVERNMENT
France's five-month-old, centre-right government warned it would take action to prevent a repeat of those bitter conflicts that crippled key industries and disrupted trade.
Police were deployed to protect border posts and key sites like the Genevilliers river port near Paris, a hub for fuel and pharmaceutical distribution to the capital and abroad. Drivers at Genevilliers said trucks were queuing up not because of protests but due to checks of every truck by police.
Police were mobilised in Strasbourg in eastern France to ensure a trade route across the Rhine into Germany remained open and stood by at other strategic sites such as the Ambes and Bassens fuel depots near Bordeaux.
"The lads are very mobilised, they are going for it," CFDT union member Maxime Dumont said.
The CFDT and CGT, which together represent over half France's unionised truckers, rejected an employer offer of a 14 percent pay rise over three years, but the offer late on Sunday that was accepted by smaller unions.
Those four unions -- the FO, CFTC, CGC and FNCR -- were to put the offer to their delegates on Monday. "We believe it's time to calm things down," said Thierry Douine of the CFTC.
French hauliers, who say profits have been cut by cut-throat competition and "social dumping" by foreign firms that hire cheaper labour in central Europe, refused worker demands to pay a 13th month salary, a common form of bonus in France.
Previous blockades hit well beyond France which has borders with six countries and ferry and tunnel links with Britain. After previous disputes, London, Brussels and Madrid demanded compensation for lost haulage and export business.