The Earthquake Recovery Minister says the rebuild of Christchurch's underground infrastructure will be quite a bit more expensive than has been predicted.
Gerry Brownlee said on Friday he does not know how much more will have to be spent, because the cost of about half the work is unknown.
The minister's comments come after details emerged of a private meeting he held with the Christchurch City Council in December last year.
Mr Brownlee said the rebuild of the city's roads and underground infrastructure was initially expected to cost about $2 billion, but workers are discovering more quake damage.
He would not be drawn on where the extra funding could come from, but said the Government and the council are in ongoing negotiations about who will pay for what.
Councillor Glenn Livingstone suggests the money could be found by cutting back on the scale of some of the city's key projects such as the convention centre or the covered stadium.