The reduced total estimate of 7.232 billion pounds ($11.688 billion) comes after 20 million ($32.3 million) pounds was cut from the budget of the main stadium, including 7 million pounds ($11.3 million) saved by scrapping a planned fabric wrap around the venue.
Olympic Delivery Authority chief executive David Higgins said organizers have saved a total of 750 million pounds ($1.218 billion) since construction began.
He said nearly 75 percent of the venues and infrastructure were complete in the Olympic Park in east London, with the roof of the handball arena the latest to be finished.
The track cycling arena, or velodrome, is set to be the first venue completed in the park early next year.
“We are in the home straight but are not complacent and are focused on maintaining progress in the months ahead,” Higgins said.
The cost of the aquatics center could rise by 11 million pounds ($17.8 million) as work is speeded up to hit the completion date of July 2011. The complexity of completing the wave-shaped roof - the architectural showpiece of the Olympics - was blamed for the added costs.
During the period covered by the report - July 1 to Sept.
30 - 39 million pounds ($63.1 million) was used from the original 2.747 billion contingency fund. There is 1.143 billion pounds ($1.8 billion) in contingency remaining.
The total public sector budget for the Olympics is 9.298 billion pounds ($15 billion) - triple the original estimate when London successfully bid to host the games in 2005.