Organisers of Chelsea Manning's speaking tour remain hopeful a ban on the convicted US whistleblower entering Australia will be overturned.
Ms Manning was due in Sydney on Sunday, but Think Inc. has received a notice of intention to deny the former soldier entry into Australia on character grounds.
Instead, Ms Manning will be interviewed via video link from Los Angeles by prominent Australian journalist Peter Greste, who will be at the Sydney Opera House.
Think Inc. director Suzi Jamil said she feels "a bit defeated" by the developments.
Ms Jamil is still waiting on a final decision about Ms Manning's situation from the Department of Home Affairs and she is hoping any delay is not intentional.
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"We're aiming to get her to be here for the Melbourne show (on September 7)," Ms Jamil told AAP.
"I can do it over video link - but Chelsea is free, she's not in prison and doesn't have to hide away in Russia."
Sydney Opera House Antidote Festival director Edwina Throsby said she was "disappointed" Ms Manning couldn't appear in person.
"Nevertheless we are pleased that Sydney audiences will still have the opportunity to hear her directly," Dr Throsby said in a statement on Friday.
Ms Manning will be in conversation with Mr Greste about data privacy, surveillance, imprisonment, the suppression of information and ideas by power-structures, and transgender rights.
New Zealand confirmed on Friday it had given Ms Manning special dispensation to apply for a visa to speak in Wellington on September 9 despite opposition calls to ban her.
Calls for Ms Manning to be allowed into Australia are growing louder, with a change.org petition receiving more than 16,000 signatures in only a day.
Greens leader Richard Di Natale has written to Mr Coleman and Home Affairs Minister Peter Dutton, declaring Ms Manning "is not a public figure who incites violence or hate".
Under Section 501 of the Australian Migration Act, a visa may be cancelled if a person does not pass the "character test".
"Australians have indicated their strong interest in hearing what Ms Manning has to say," Senator Di Natale wrote.
"To deny her the opportunity to speak to our community is unfair and unwarranted."
The Australian Lawyers Alliance and Amnesty International accused the government of trying to silence Ms Manning.
The Department of Home Affairs said it does not comment on individual cases but all non-citizens entering Australia must meet character requirements set out in the Migration Act.
"A person can fail the character test for a number of reasons, including but not limited to where a non-citizen has a substantial criminal record or where their conduct represents a risk to the Australian community," a department spokesperson said.
Ms Manning was banned from entering Canada last year due to her criminal convictions in the US, but was allowed to speak in Montreal in May.
She served seven of her 35-year prison sentence for leaking more than 700,000 classified military and diplomatic documents.
Then-president Barack Obama granted her clemency in 2017.
