Culture Secretary Tessa Jowell said today she was trying to settle the budget for the 2012 Olympics as quickly as possible amid claims projected costs are continuing to spiral.
She admitted the Government did not know precisely how the London Games would be funded but stressed that organisers were ahead of schedule compared to previous Olympic cities.
The budget for the Sydney Olympics was settled just two years before they took place, she said.
Her comments came as the Olympic Delivery Authority (ODA) was reportedly drawing up a budget of £5.1 billion for the London Games - more than double the original estimate.
Ms Jowell said today there was "nothing new" in that claim, adding the budget would have to cover contingencies.
Whitehall spending watchdog the National Audit Office warned last week the lack of a final agreed budget at this stage was a "major risk" to success.
Ms Jowell could today only say the money would come from "a number of sources" of both public and private cash, adding: "I would like to get this settled as quickly as I can."
She went on: "I'm quite sure people are getting impatient about the length of time it's taking to settle this.
"I would only say that this is five years before the games - Sydney did not settle their budget until two years before they hosted the most successful Games ever."
The £5.1 billion figure was reported today by The Sunday Times, which said the Government would have to raise £1.7 billion from lottery money.
Ms Jowell told BBC1's Sunday AM: "There is absolutely nothing new in the Sunday Times story."
Asked whether the Games would cost £5.1 billion, she added: "That is not the case at this point, because we are still, within Government, negotiating both the likely cost of the Olympics and the funding requirement.
"And I draw a distinction, because there will certainly have to be provision for contingency.
"But I think you will see over the next two to three years extremely wild claims about what the Olympics are going to cost."
Shadow culture minister Ed Vaizey said the new figures came as no surprise.
"The budget is completely fluid and what the Government needs to do is come clean about what they think it will cost and also how they will fund it," he said.Reuse content