* Anti-pension strikes to widen in 6th big protest
* Fuel supplies tighten, govt taps emergency reserves
By Catherine Bremer
PARIS, Oct 19 (Reuters) - Striking public sector workers will likely gridlock travel in France on Tuesday and protesters will take to the streets en masse as trade unions test President Nicolas Sarkozy over his unpopular pension reforms.
Airport staff, bus and train drivers, postal workers and the armoured truck drivers who stock cash machines were expected to join refinery workers and others in a day of nationwide strikes against Sarkozy's plan to raise the retirement age.
The authorities will be especially alert for any signs of Monday's sporadic outbreaks of violence in some cities, that saw small groups of protesters torching vehicles and scuffling with riot police.
Tuesday will be the sixth day of nationwide strikes and protests since June and a last-ditch challenge to the centre-right government before a final Senate vote this week on the pension bill, which the government says is vital to rein in a ballooning pension shortfall as the population ages.
On Saturday, the last national day of protest, an estimated million or so people demonstrated.
Tuesday's day of protest comes on top of week-long strikes at refineries, blockades of some fuel depots and an unrelated oil port strike which have sucked dry hundreds of petrol pumps, triggering panic buying and queues of motorists. The government has been forced to tap strategic industrial reserves.
Sarkozy, who is meeting his German and Russian counterparts for talks in the northern French seaside town of Deauville on Tuesday, told reporters late on Monday he would not back down. "The reform is essential and France is committed to it and will go ahead with it just as our German partners did," Sarkozy said after talks with German Chancellor Angela Merkel, who urged the French to accept that living longer meant working longer.
Germany voted in 2007 to lift its retirement age to 63 from 62 by 2029 and many other European countries have similarly increased retirement ages, or plan to.
Opinion polls show a majority of French resent the plan to raise the minimum and full retirement ages by two years to 62 and 67 respectively, and feel they are being punished unfairly for a failure in France's cherished social security system.
The unions -- which crushed pension and labour reforms in 1995 and 2006 with long-running protests -- say they want the bill scrapped and a say in discussing a pension overhaul.
"(There could be) problems with cash supply at bank branches if the government refuses dialogue," Pascal Quiroga, a CFDT union representative in the cash transit sector told daily Les Echos, as armoured truck drivers were called in to strike.
So far the transport strikes have not been severe enough to paralyse France, however, the refinery strikes are a serious threat. As fuel depots dry up, France will become increasingly dependent on strategic reserves which need to be accessed and trucked across the country -- a logistical headache.
Sarkozy hopes the Senate will approve his bill by Friday after which it just needs a last vote by a joint parliamentary committee. Unions have vowed to keep protesting regardless. (Editing by Matthew Jones)