South Australia's reduced share of national GST will present a challenge at next year's state budget, Treasurer Rob Lucas says.
But Mr Lucas praised the $2.6 billion in new capital infrastructure commitments included for the state in the 2019/20 federal budget.
"There's a whole series of metropolitan and country transport projects which have been committed to in this particular budget which haven't been announced yet, and they are very significant," he said.
The budget also included $2.7 billion to finish the North-South corridor upgrade, as investigations into possible tunnels continue.
It revealed the state's share of national GST will drop from $7.3 billion predicted in the state budget to an expected $6.8 billion.
Mr Lucas assured South Australians this year's budget will still balance, despite a deficit inherited by the new government from Labor.
"Next year's budget, with a $500 million write-down in the GST, is going to be a real challenge and we'll have to consider what our response is over the next couple of months," he said.
"The size of the national GST pie is actually smaller than predicted, and South Australia's share is going to be smaller because of a decision of the independent Grants Commission."
Treasurer Josh Frydenberg delivered his first federal budget, featuring the first surplus in more than a decade, on Tuesday night.
Mr Lucas dismissed suggestions the government had concentrated funding on the marginal seats of Boothby and Mayo in a bid to win over voters ahead of the federal election.
"There are big commitments to projects in all seats, right across metropolitan and regional South Australia," he said.
