ABC's 7:30 host Leigh Sales wasn't thrilled with the current Federal Budget and grilled Treasurer Josh Frydenberg on Tuesday night about the range of "assumptions".

“The budget is based on a series of assumptions, and they are that the whole Australian population will be vaccinated by the end of the year, that there’ll be no sustained state border closures this year and no major COVID outbreaks, and that international borders will start to operate reasonably normally by the middle of next year,” Sales said.

“Those are very uncertain and heroic assumptions, aren’t they?”

Frydenberg said that the government is staying cautious due to the coronavirus pandemic.

“We’re in the middle of a pandemic, and making assumptions during normal times is difficult – to make them during the middle of a pandemic is even more so,” he said.

“Those assumptions are based on the best available evidence to us.

“We know that more than 10 per cent of the Australian population has now received their first dose.

“We’ve seen 30 per cent of those aged over 70 or above receive a dose.

“We saw more than 400,000 doses rolled out over the course of the last week. More supply is coming online. So that is the assumption about vaccines.

WATCH: Treasurer @JoshFrydenberg joins @leighsales for his first post-budget interview, after he declared Australia's economic engine is "roaring back to life" and unveiled tens of billions in new spending. https://t.co/Hny0pkGhKf

— abc730 (@abc730) May 11, 2021

“With respect to international borders, it’s quite a conservative, cautious assumption that international borders will gradually reopen from the middle of next year.”

It's been a slow start to the national vaccination program, with numbers trailing behind what's required.

“The mass vaccination centre will be able to administer up to 30,000 vaccines per week once it is up and running, that means around 5000 vaccinations per day,” NSW Premier Gladys Berejiklian said.

“The centre, combined with the more than 100 NSW Health run clinics and hubs, means NSW Health can administer around 60,000 vaccines each week across the state.”

50 million doses are required to vaccinate everyone over the age of 16 in Australia, but authorities have managed to deliver 2.7 million doses.