Treasurer Josh Frydenberg told reporters in the federal budget lockup on Tuesday that all willing Australians would receive two doses by December 31.

That will require the weekly pace of the rollout to triple.

But the prime minister is keen to point out it is not a concrete commitment.

"There are assumptions that go to the rollout. They are not policy settings," Mr Morrison said on Wednesday.

"We will continue to roll the vaccine out, as we have been, and accelerating it from next week. We will continue to do everything we possibly can to ensure we're progressing that vaccination program."

Labor health spokesman Mark Butler asked in parliament why a clear answer could not be given on when all Australians would be vaccinated.

Health Minister Greg Hunt said the government was seeking sufficient doses this year to guarantee supply for the population to be offered vaccination.

As of Wednesday, there had been 2.81 million jabs given, including 76,379 in the past day nationally.

The government will spend an extra $1.9 billion over the coming year to boost its vaccine supply to 170 million doses and speed up the rollout.

The budget also contained funding to expand the Howard Springs quarantine centre, but there was no money for a Victorian quarantine proposal.

The prime minister is not ruling out financially backing the Victorian project.

"The Victorian government has put forward a very good proposal and we're working through the detail of that right now," he said.

"We will see how we can work together on that initiative."

The Northern Territory's Howard Springs facility, which is housing Australians returning from overseas, is slated to cost $487 million over two years as it expands to 2000 places.

The budget papers also confirmed a plan to investigate domestic manufacturing of mRNA vaccines, although an exact funding figure was not divulged due to "commercial in confidence sensitivities".

Finance Minister Simon Birmingham says the federal government is in negotiations with global pharmaceutical companies to bring their mRMA vaccine technology to Australia.

He said money was baked into the bottom line of the budget to invest in manufacturing mRNA vaccines.

However, the government has not yet outlined its proposed spending commitments.

"It's part of the contingency reserve in the budget - we just don't publish those figures because obviously we want to negotiate the best possible deal for the taxpayers," Senator Birmingham told Sky News.

He said negotiations with vaccine companies and firms seeking to establish a production facility were sensitive.

Treasury also expects international travel to "remain low" through to mid-2022 before a gradual recovery in international tourism.

In response, Qantas announced on Wednesday it had delayed its planned resumption of international flights until late December.

The airline was due to restart services at the end of October.

Australian Associated Press