(Updates with Senate approval of legislation) MEXICO CITY, Dec 10 (Reuters) - The Mexican Congress late on Wednesday passed one of the biggest overhauls to the country’s pension system in years, boosting retirement benefits and reducing workers’ mandatory contribution times, in a victory for President Andres Manuel Lopez Obrador. The initiative, which the government originally set out in July, will lower to 1,000 from 1,250 the number of weeks workers must have paid in to claim retirement benefits. It caps the fees pension funds can charge, and increases employers’ contributions to pension pots as part of a hike in workers’ total contributions, to 15% of salary from 6.5%. The law also raises the sum workers are guaranteed to receive. Passed by the lower house in the afternoon, the bill moved to the Senate and was fast-tracked for rapid approval by the floor of the upper chamber on Wednesday night. The legislation will now pass to Lopez Obrador for its promulgation. (Reporting by Noe Torres; Editing by Dave Graham and Alex Richardson)