National says the previous Government's planned spending on KiwiRail will have to be reduced.
It says commitments made by Labour when it was in power total more than $3 billion.
Finance Minister Bill English says rail needs a good going over to make sure that a deal that was done in a different world, and was far too generous, is one that can be met now.
On Monday, the Government approved more than $115 million for 17 passenger carriages and 20 locomotives.
The funding will come from existing budgets and borrowing. The carriages will be built in Dunedin and the locomotives in China.
The Rail & Maritime Union says it's disappointed that the new locomotives will be built in China.
However, general secretary Wayne Butson says the union understands the logic behind the decision.
He says it would be difficult to build the locomotives in New Zealand in the time frame required.
