Lord Coe has admitted it is still unclear what the final cost of staging the 2012 Olympics will be.
Coe has welcomed an English bid for the 2018 World Cup
He told BBC Radio Five Live he was in charge of raising £2bn of private money to stage the event.
But the cost of building the venues would come out of the public purse - and that figure was yet to be agreed.
"I will be pleased when we get that figure. That figure has to be sustainable and it has to be robust," he said.
"We want transparency and we will get transparency.
"For very good reason I'm not going to get into figures, be it £5m, £6m, £10m and before we know it it's £20bn and it's bigger than Beijing, and all that."
He also emphasised the need for areas outside London to be part of the 2012 experience.
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"I am acutely conscious that this is seen as a UK-wide project," he said.
"Of course London is at the centre of it but what I think we are doing is bringing London up to the standard per head of population that most of the other regional cities like Birmingham, Manchester and Sheffield are enjoying.
"We've asked for UK-wide submissions from communities that have sporting facilities that would like to host a team or a coach and we've had 700 applications."
He also welcomed the possibility of an English bid for the 2018 football World Cup, insisting that it does not conflict with preparations for the 2012 Olympics.
"I'm entirely happy that we should, as an ambitious sporting nation, as and when we can host sporting events, we should bid for them," he said.
"As I said we want to use the Games as a catalyst for other events. There is room for a World Cup and an Olympic Games."