Sydney Airport announced Monday it had agreed to a US$17 billion takeover bid by an Australian investor consortium, just days after reopening to international travel.

The airport's board unanimously approved the sale to the Sydney Aviation Alliance -- a consortium of infrastructure investors and Australian pension funds -- and recommended shareholders vote in favour.

The alliance offered Aus$8.75 per share, or Aus$23.6 billion (US$17.5 billion), after its earlier offers in recent months were rejected as too low.

"Today's announcement is the culmination of months of engagement between all parties," Sydney Airport chairman David Gonski said in a statement.

"The Sydney Airport Boards believe the outcome reflects appropriate long-term value for the airport."

The announcement comes in the wake of Australia's international border partially reopening, almost 600 days after one of the world's toughest pandemic border closures began.

Vaccinated Australians travelling via Sydney and Melbourne may now come and go without quarantine or obtaining an official exemption -- with the move seen as the country's first step in the gradual resumption of travel.

The airport sale remains subject to conditions, including an independent expert evaluation.

Shareholders are expected to consider the deal at a meeting in the first quarter of 2022, with a 75 percent majority required for it to gain approval.