© Reuters. A mostly empty domestic terminal at Sydney Airport is seen after surrounding states shut their borders to New South Wales in response to an outbreak of the coronavirus disease (COVID-19) in Sydney, Australia, December 21, 2020. REUTERS/Loren Elliott/File

SYDNEY (Reuters) – A consortium led by Macquarie Group (OTC:MQBKY) is considering an offer for Sydney Airport Holdings, in a potential challenge to a A$22.3 billion ($16.7 billion) bid already on the table, Bloomberg News reported on Thursday.

Macquarie has been speaking with potential partners, including local pension funds, about making a joint offer for the airport, the report said, citing unidentified sources.

The report sent Sydney Airport’s shares up as much as 3.6% to A$7.88, as of 0139 GMT. The stock, however, still traded 37 cents lower than the A$8.25 apiece offered by a consortium of infrastructure investors on Monday, suggesting market uncertainty over deal.

The consortium of infrastructure investors – investment manager IFM Investors, superannuation fund QSuper, and fund manager Global Infrastructure Partners – offered to buy Australia’s biggest airport at a 42% premium to the stock’s Friday close.

Talks were at an early stage and Macquarie could also seek to join the IFM consortium, Bloomberg reported on Thursday.

Macquarie and Sydney Airport did not immediately respond to Reuters’ requests for a comment.

IFM holds stakes in major airports in Melbourne, Brisbane, Perth, and Adelaide. QSuper holds a stake in Britain’s Heathrow Airport, while Global Infrastructure is invested in the country’s Gatwick and London City airports.

($1 = 1.3358 Australian dollars)