Oil refineries have been shut for a week, hundreds of petrol stations have run dry and a further day of national strikes is under way.
Mr Sarkozy says reform is "essential" and "France is committed to it".
But with the Senate due for a final vote this week, protests are planned in more than 200 towns and cities.
The French government wants to raise the retirement age from 60 to 62 and the full state pension age from 65 to 67.
But the plans are widely unpopular with the public and left-wing senators have submitted hundreds amendments in an attempt to delay the vote.
Although the bill was initially expected to be passed on Wednesday, some reports say the debate could last until the weekend.
Tuesday will see France's sixth national day of protests since early September with further disruption expected to air travel, trains and schools.
Half of flights in and out of Paris's Orly airport have been cancelled and 30% of flights at other airports have been affected.
One opinion poll on Monday suggested that 71% of those surveyed supported the strikers, despite the increasing effect on people's lives.
One in four petrol stations at supermarkets are said to have run dry or are on the verge of closing and oil company Exxon Mobil has described the situation as "critical".
A spokeswoman said that anyone looking for diesel around Paris or in the western area of Nantes would face problems.
Severe shortages have been reported in Brittany in north-west France and the International Energy Agency says that France has begun tapping into its emergency oil reserves.
Workers at France's 12 oil refineries have been on strike for a week and entrances to many of the country's fuel distribution depots have been blocked.
Panic-buying has been blamed for a 50% increase in fuel sales.
Lorry drivers joined the protests on Monday, staging a go-slow on motorways around several cities.
Dozens of oil tankers are anchored off the coast of Marseille because of a strike at two Mediterranean oil ports and, inside the city, rubbish has piled up because of a strike by refuse collectors.
There were protests outside hundreds of schools on Monday and students and youths took part in a number of street demonstrations.
In the western suburb of Nanterre in Paris, dozens of youths clashed with riot police who fired rubber bullets.
Shop windows were reported broken in the Saint-Denis suburb, where education officials said more than half the area's secondary schools had been blockaded.
French President Nicolas Sarkozy has ordered key ministers to form a crisis cabinet with the role of ensuring the continuity of fuel supplies.
Three departments are being charged with coordinating the state's services to maintain the supply: the interior and economy ministries as well as the energy and environment department.
The head of the French Petrol Industries Association, Jean-Louis Schilansky, has said fuel shortages are not yet at crisis point.
"If the lorry drivers go on strike, if people block the refineries, then we will have a very big problem. But we're not at that stage yet," he said.
France has a strategic fuel reserve which holds up to three months of supplies, the government says.