The Federal Government is preparing to ban US whistleblower Chelsea Manning from coming to Australia for a speaking tour.

Key points: Chelsea Manning is scheduled to give speeches in Sydney, Brisbane and Melbourne

Chelsea Manning is scheduled to give speeches in Sydney, Brisbane and Melbourne The Federal Government has issued a notice of intention to refuse her visa

The Federal Government has issued a notice of intention to refuse her visa Tour organisers have called on supporters to send letters to the Immigration Minister

The former soldier-turned-whistleblower spent seven years behind bars, including 11 months in solitary confinement, for sending nearly 750,000 classified military and diplomatic documents to WikiLeaks.

She is planning to give a speech at the Sydney Opera House on Sunday night before similar talks in Brisbane and Melbourne.

The Australian organiser of her speaking tour, Think Inc, has written to supporters asking them to lobby the newly installed Immigration Minister, David Coleman.

"We have just received a Notice of Intention to Consider Refusal under s501 of the Migration Act from the Australian government in regards to Chelsea's Visa," the company's director Suzi Jamil wrote to supporters.

"We are looking for support from relevant national bodies or individuals, especially politicians who can support Chelsea's entry into Australia.

"We are seeking letters of support to send to the Minister for Immigration in order for him to reconsider his decision."

'Character requirements'

Section 501 of the Migration Act allows the Minister to deny anyone a visa if they do not pass "the character test".

The Home Affairs Department would not comment on Ms Manning's case.

A spokesman said all non-citizens need to meet certain character requirements before being granted entry to Australia.

"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," the spokesman said.

Ms Manning, a transgender woman, is also planning to speak in New Zealand, where the centre-right National Party is lobbying for her visa to be cancelled.

She was banned entry to Canada in 2017, although she was permitted to speak at an event earlier this year.

Sorry, this video has expired Chelsea Manning discusses her concerns over Australia's immigration system

'So far from a risk'

Greg Barns, a lawyer for Wikileaks founder Julian Assange, said refusing her entry was extraordinary given her sentence had been commuted.

"There have been in the past many people who've come to Australia with criminal records … and she should be no exception," Mr Barns.

"I don't think anyone would seriously suggest Chelsea Manning while in Australia would be rummaging through the files of the Department of Foreign Affairs and Trade or Defence or the US Embassy.

"Those provisions are really designed to be utilised in cases where there is a risk that a person may commit offences, is a risk to the Australian community, no one would seriously suggest that's the case here."

Ms Jamil said Ms Manning was "so far from a risk to the Australian public".

"In January 2017, the incumbent President Obama commuted Chelsea's sentence. That should be a consideration in this instance," Ms Jamil said.

"We're still really positive about the whole situation and we want to do everything in our power that we legally can in order to provide the reasoning behind why Chelsea should be able to enter our country."

But James Brown, a non-resident fellow at the United States Study Centre and a former Australian Army officer, told ABC News it was a "textbook case" and Ms Manning shouldn't be allowed to enter Australia.

"Coming into Australia as a non-citizen is a privilege, not a right. And someone who has a substantial criminal record shouldn't enjoy that right, and particularly someone who has worked to undermine our national interest and the security of our troops," he said.

He says it is not a freedom of speech issue.

"No-one is saying you shouldn't read her books, or her columns in The Guardian, or watch movies in which she features. We have the right to determine who comes into Australia, and we shouldn't have someone who has actively worked against our national interest," he said.

Sorry, this video has expired Chelsea Manning says people want her to not "shut up".

In 2010, Ms Manning was sentenced to 35 years in prison for leaking more than 700,000 documents to WikiLeaks — the biggest breach of classified data in the history of the US — after being found guilty of espionage.

The documents included more than 250,000 diplomatic cables rom US embassies, a "collateral murder" video of a US Apache helicopter which killed civilians in 2007 and confidential files related to 779 Guantanamo Bay detainees.

During the case Ms Manning's defence argued she was not a traitor but rather a "young, naive and good-intentioned" citizen who wanted to encourage public debate.

But the prosecution said she recklessly betrayed her uniform and country by leaking documents she knew Al Qaeda would see and use.

She came out as transgender shortly after her sentencing, but the military denied her request for hormone therapy treatment while behind bars.

She was placed in solitary confinement after attempting suicide twice.