Malcolm Turnbull says a global ratings agency has delivered a "timely warning" on the need to repair the federal budget.
While Standard & Poor's confirmed Australia's top-tier triple-A credit rating last week, the global ratings agency also left the outlook on negative.
This reflected S&P's view of the "significant uncertainty" around the ability of the budget returning to surplus in the early 2020s as repeatedly promised by the government.
The prime minister said while setting a path to surplus in 2020/21 was of "great credit" to Treasurer Scott Morrison, the rating's agency had issued a timely warning.
"The warning about the challenges of budget repair were very real," Mr Turnbull told News Corp's Miranda Devine Live program on Monday.
"We've achieved a great deal of budget repair through the Senate but not as much as we would like."
He said getting the budget back to balance was critical to the size and scope of any personal income tax cuts this year.
"We are not going to sacrifice our return to surplus - that is the top priority," Mr Turnbull said of the possible middle-income tax cuts.
"How much and the timing of it and the scale of it is going to depend on what is affordable, consistent with bringing the budget back into balance."
