* Refinery strikes to hit fuel depots by mid-week
* Senate due to vote Wednesday on pension bill
* Fresh protest on Tuesday to keep up pressure
By Catherine Bremer
PARIS, Oct 17 (Reuters) - French President Nicolas Sarkozy is facing a make-or-break week for his unpopular pension reform as rail and refinery workers, truck drivers and street marchers ramp up pressure to scrap it before a crucial Senate vote.
Throughout months of opposition to his plan to raise the retirement age in France, to rein in a ballooning pension deficit, Sarkozy has vowed not to cave in to the country's powerful unions.
The unions, who have a history of crushing reform, have vowed to match his resolve.
With petrol pumps drying up, truckers threatening to block key roads and the public planning more nationwide marches, this week will put the president's ambition to the test.
If strikes running since Tuesday at all 12 of France's refineries continue, petrol pumps could start to run dry by mid-week, according to the UFIP oil industry lobby, meaning the government would have to consider tapping emergency reserves.
So far, less than two percent of France's petrol stations have been affected, and the country's main airports have enough fuel to continue operating indefinately.
Fears that France's main international airport Roissy Charles de Gaulle could run out of fuel in the next 48 hours were dispelled by Transport Minister Dominique Bussereau who told Europe 1 radio on Sunday that the supply pipeline to the airport was working.
"There is no concern about Roissy. We can feed it (with fuel) for an unlimited period of time," he said.
But all of France's refineries remained on strike and 350 to 400 petrol stations run by oil company Total were suffering supply disruptions.
Shortages could hit transport much harder if truckers manage to halt road transport on Sunday night and Monday and if protesters hit the streets in force on Tuesday, the day before the Senate is due to vote on Sarkozy's bill.
If the Senate votes in favour, the bill would go to the president for his signature, possibly as early as Friday.
Turnout at nationwide demonstrations on Saturday was lower than at previous rallies, according to the government, which read that as a sign its message is getting through. The unions said up to 3 million people had participated.
"I think we're clearly at a crossroads. What I hope is that reason will prevail and that this reform can be adopted in the coming days and implemented in the coming weeks," Minister of Agriculture Bruno Le Maire told Europe 1 radio.
Unions are betting the next in a series of street protests since the summer will have more clout if combined with fuel shortages, cancelled trains and trucker disruption on roads.
Truck drivers -- the big guns of French protests because of their ability to block off major highways and disrupt the transport of vital goods like food -- will start to block roads from Sunday evening, a union spokesman said.
UNIONS SAY WON'T GIVE UP
Leaders of France's powerful unions say they will not give up until the government drops the bill and invites them to the table to have their say in a pension overhaul.
Charles Foulard, the CGT union coordinator for Total, told Reuters on Saturday that striking refinery workers had no intention of conceding.
"There is toughening of resolve," he said. "The truck drivers are going to join us ... We will go till the end."
Most of France's fuel depots, which are mainly outside refineries, have a couple of weeks' supply, but depots in southwestern France are already depleted because a three-week unrelated strike at a major oil port near Marseille has hit supplies of crude into refineries in the area.
Unions plan to meet on Thursday, a day after the Senate vote, to discuss further action.
(Editing by Michael Roddy)