The Prime Minister says the Budget will reveal the Government is on track to getting its books back into surplus in 2014-15.
However, John Key acknowledges that economic uncertainty in Europe has increased and that poses a risk to the Government's objective.
Since the Treasury finalised its economic forecast for the Budget at the end of April, the situation in Europe has got worse.
Mr Key says he would not be happy to delay getting back to surplus, but it could be taken out of the Government's control if the European crisis causes the world economy to slow even more.
He says in that situation, he would not support making deeper spending cuts just to get back into surplus in 2014-15.
The problems in Europe vindicate the Government's commitment to getting its finances back into shape, he says.
The Budget will be delivered on Thursday afternoon.