Nicolas Sarkozy said the minimum retirement age, which, in his view, is the main element of the reform, will be gradually raised from 60 to 62 by 2018.
French law provides for a maximum age limit beyond which workers have to retire. This age limit will also be raised from 65 to 67.
Unions and political opponents say the reform plan, which aims to reduce France’s high budget deficit, puts an unfair burden on workers.
Tuesday’s strike disrupted transport, shut schools and brought more than a million into the streets.
Reacting to Tuesday’s protests, Sarkozy announced some concessions in the reform bill.
Workers starting younger than 18 and making pensions contributions for the required number of years would still retire at 60 "or even sooner”, Sarkozy said.
He also offered to broaden opportunities for workers in physically demanding jobs to apply for earlier retirement.
Unions on Wednesday said Sarkozy’s proposed improvements were “insufficient” and are discussing possible further action.
Socialist leader Martine Aubry told France 2 television that the reform was both unjust and ineffective.
The government says the reform can save 70 billion euros by 2030 at a time when France's public deficit is around eight per cent of GDP - well above the eurozone target of three per cent.
Sarkozy said the only alternative would be to lower retirement pensions or significantly raise taxes, which he thinks would leave workers worse off.
At 62, the minimum retirement age would still be well under the average of around 64 in the OECD group of wealthy democracies.
But the French also pay high tax on their salaries, and are among the world’s most productive workers on an hour-by-hour basis, the OECD says.
Sarkozy’s personal approval rating - around 34 per cent according to several polls - is at an all-time low, two years before the 2012 presidential election.
The proposed pension reform bill is pending in the National Assembly, France’s lower house of parliament, until 15 September.