Construction work continues on the Olympic Park in Stratford, east London
The amount of money needed to ensure London's Olympic Park has a lifespan beyond the 2012 Games remains unclear, Olympics minister Tessa Jowell says.
It was "difficult to be precise" until further planning had been done, she told a committee of MPs.
About £450m is thought to be needed to convert the venue after the Games but this was still a "highly provisional approximate figure", she added.
The cost is not covered by the existing £9.3bn Olympic budget.
Instead, the funding is expected to come from central government, the Department for Communities and Local Government or City Hall - or a combination of the three.
So far £350m has been set aside to ensure the park, in Stratford, has a legacy which benefits east London for many years to come.
But even more money could be required for this purpose, Ms Jowell told the Commons Culture, Media and Sport committee.
"Until the masterplan is confirmed and the phasing of development is confirmed, it is difficult to be precise," she said.
Communities Minister Shahid Malik, who also appeared before the committee, said it was "premature" to discuss a figure at this stage.
"We need the legacy masterplan in place then we can look at what funding requirements might be," he said, adding he was "confident" the money would be found.