The airline was due to restart services at the end of October but on Wednesday pushed back the date.

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

Qantas believes the new assumption would ready the company to take advantage of tourism and trade in a post-coronavirus world.

"We remain optimistic that additional bubbles will open once Australia's vaccine rollout is complete to countries who, by then, are in a similar position, but it's difficult to predict which ones at this stage," it said in a statement.

Treasurer Josh Frydenberg stressed the border timeline was his department's assumptions rather than government policy.

"We will open the international borders when it's safe to do so," he told the National Press Club.

"We cannot afford to take the risk right now to open our borders in a way that would compromise the health of Australians."

He said small cohorts of international students were expected to arrive from the end of this year before borders gradually open from mid-next year.

Qantas will continue providing repatriation and freight flights from overseas.

Customers who booked international tickets for travel between October and December will be contacted by Qantas.

The company says it will keep reviewing its plans in the lead up to December.

Flights to and from New Zealand are unaffected.

Australian Associated Press