* Unions hope demonstrations will add to pressure on govt
* Unions estimate 2.9 million, police 899,000 on streets
* President Sarkozy says raising retirement age is essential
(Adds Labour Minister in paragraph 12)
By John Irish
PARIS, Oct 2 (Reuters) - French families, students and private sector workers joined mass demonstrations on Saturday as trade unions ramped up pressure on the government to drop pension reforms.
Opposition to President Nicolas Sarkozy's plan to raise the retirement age to 62 from 60 showed no signs of abating and hundreds of thousands across the country marched in the fourth round of rallies in as many months
Unions said that about 2.9 million had marched, while police said the crowds numbered 899,000. The union figure was about the same as at the last demonstrations on Sept. 23. The police figure was slightly lower.
About 230 protests took place across the country with a bigger turnout of families, who are less likely to protest on weekdays, and students as concerns about pension reform highlight a deeper anxiety about their future.
Until now the protests have been also mostly in the public sector but private sector workers including some from plane builder Airbus EAD.PA and national carrier Air France-KLM (AIRF.PA) joined Saturday's marches.
"We are a lot more today than during the week," said Xavier Petrachi, a delegate at the CGT union in Toulouse. "It's got a real family feel, buggies are out. France is protesting."
The draft bill, a reform deemed unjust by unions but essential by Sarkozy, will be debated in the Senate -- the upper house -- from Oct 5.
A survey published by French daily newspaper L'Humanite showed more than 70 percent of people backed the day of action.
Trade unions across Europe are seeking to rally opposition as governments slash spending to dig their way out of debts run up during the global financial crisis. [ID:nLDE68L1DE] [ID:nLDE68J1RW]
"We need a show of strength," said Jean-Claude Mailly, head of the more radical Force Ouvriere union. "The government is frozen ... they are under the thumb of financial markets."
The government says its legislation is essential to erase a growing deficit in the pay-as-you-go pension system, curb rising public debt and preserve France's AAA credit rating, which enables it to borrow at low financial market rates.
French Labour Minister Eric Woerth late on Saturday told France 3 television the government still had to educate people about the reform, but it would not budge on its core.
SARKOZY STANDS FIRM
Unions hope the turnout will oblige the government to back down over the flagship reform of Sarkozy's five-year term, which would also raise the age at which people can retire on a full pension to 67 from 65.
"We won't back down," said Bernard Thibault, head of the powerful CGT union. "If the government won't listen there will be further action."
Force Ouvriere and the radical Sud Rail are pressing for rolling strikes, which the larger unions have yet to decide whether they will support. A new strike is already planned for Oct. 12. It remains to be seen whether workers will sacrifice more days' pay to test a government which appears resolute.
The Senate has said it will offer concessions, but has ruled out any changes to key features. The reform is a major part of the government's plan to balance the system's finances by 2018.
The unions and the left-wing opposition say the plans to raise the retirement age, raise civil servants' contributions to private sector levels and make people work longer for a full pension are unjust.
"I am listening to the protesters, I understand their anger, but the role of the head of state is to fulfil his responsibilities," Sarkozy said on Friday. "The pension reform and budget cuts are essential for our competitiveness."
Striking dockers continued to paralyse the country's largest port in Marseille on Saturday, while Corsica's main cities halted the sale of diesel due to low stocks.
(Additional reporting by Gerard Bon and Laure Bretton; editing by Andrew Roche/Ruth Pitchford)