Westpac chief economist Dominick Stephens says he expects Treasury forecasts in this week's Budget will be overly optimistic and we won't see debt levels fall to that targeted by Finance Minister Bill English.
English has indicated he wants to drop New Zealand's net government debt from 26 per cent of GDP to 20 per cent by 2020.
The Budget would lay out a timeline of "good government revenue and falling government debt", Stephens said.
But Stephens said he would greet that kind of optimistic outlook with some scepticism.
"I'm not so sure the economy will be that strong later in the decade."