PARIS — Strikers defying President Nicolas Sarkozy's push to reform France crippled the country's public transport system Thursday, forcing commuters to drive, pedal or walk to work — or stay home. Some workers vowed to continue the walkout Friday.

The strike was the first major showdown between Sarkozy, who was elected in May with a strong mandate for change, and powerful unions, who have in the past forced the government to back down from reform plans.

Bus, train and subway service ground to a halt across France: More than 90 percent of high-speed TGV trains weren't running; only one Paris subway line — which is automatic, with no drivers — was running as usual; and international trains were affected though spared the worst.

"Am I for it? Non! They infuriate us," Charlotte Ardant, a perfume industry worker, said of the unions. She said she slept at a friend's house last night to be closer to her office.

The economic impact and the full extent of the strike was virtually impossible to estimate right away.

Employees at Paris' transport authority agreed to extend their walkout — originally scheduled to end Thursday evening — until Friday on at least six of 14 subway lines, the UNSA labor union said. Others were also considering whether to follow suit.

Unions have been in a staring match with Sarkozy's conservative government over the past several months. Thursday's walkout amounted to the first exchange of shots.

In neighboring Germany, meanwhile, commuters in the largest cities sat for hours in traffic jams after more than 1,000 train drivers walked off their jobs on the country's dense local rail network. The German strike was to last nine hours. It was the second such action organized by German train drivers' union GDL, which is seeking better working conditions from railway operator Deutsche Bahn.

In France, the dispute centers on Sarkozy's plans to eliminate a special pension plan devised to give advantages to those in physically demanding jobs, such as miners and train drivers. Workers covered by those pensions are able to retire earlier — and on more generous terms — than the vast majority of France's working population.

The president wants a level playing field for workers: 40-year contributions into the pension fund to obtain full retirement benefits. Sarkozy has been eager to rein in state spending.

He has also sought to reduce the power of extended union action, championing a law that would force workers to provide at least a minimum level of service during strikes.

But in France, where the right to strike is widely seen as sacrosanct, even some commuters hampered by the walkout expressed their support for the transport workers.

"I agree with this strike," said engineer Annie Proy, who had to ride a subway instead of her usual bus to get to her job east of Paris. "Afterward, the government will attack the rights of other workers."

Other unions outside the transport sector have been relatively quiet about protest plans — apparently keeping their powder dry for Sarkozy's planned broader reforms of the public service sector, which could affect everything from hospitals to state-run day care.

Large numbers of people cycled in Paris during the early rush. But in the suburbs, many people appeared to have taken the day off or were working from home instead of attempting to venture into Paris.

Regional trains were virtually at a standstill, and many suburban commuters were cut off from neighboring cities by public transport and feared driving to work would ensnare them in traffic jams.

Four in five Eurostar trains to London were running, and three in five Thalys trains to Belgium and the Netherlands, said national rail operator SNCF.

Flights in and out of Paris were unaffected, said the Paris airports authority and Air France, though it added that some travelers may have had trouble getting to the airport via commuter trains.

Sarkozy was in Portugal at a EU summit Thursday. At a weekly news conference, his spokesman David Martinon said the president was being informed regularly about the strikes but referred questions to the Labor Ministry.

Labor leaders hoped the walkout would recall 1995 strikes that paralyzed the country and sapped then-President Jacques Chirac's drive for reform. Those strikes — also involving retirement rights — dragged on for three weeks.

Associated Press writers Elizabeth Ryan and Jean-Marie Godard in Paris contributed to this report.