US President Donald Trump asked Australian Prime Minister Scott Morrison for his nation's help in investigating the origins of the Mueller investigation into Russian election interference.
An Australian Federal Government spokesperson confirmed the request, which is believed to have happened weeks ago after Mr Trump criticised Australia over the investigation by former FBI head Robert Mueller.
The Mueller probe, which Mr Trump repeatedly condemned as a "witch hunt", found while there was no evidence that Mr Trump's campaign conspired with Russia during the 2016 election, it was unable to exonerate him for obstruction of justice.
A White House source confirmed that Mr Trump asked Mr Morrison to assist a Justice Department investigation into the Mueller probe being carried out by US Attorney-General William Barr.
"The Australian Government has always been ready to assist and cooperate with efforts that help shed further light on the matters under investigation," a Federal Government spokesperson told the ABC.
"The PM confirmed this readiness once again in conversation with the President."
Sources have told the ABC that Australia's ambassador to the United States, Joe Hockey, wrote to Mr Trump's chief of staff seeking an explanation after he heard the President's criticism of Australia on 25 May.
The call between Mr Trump and Mr Morrison happened months later, in the first week in September, before the Prime Minister travelled to the United States, where he met with Mr Trump in Washington and Ohio.
Australia's former high commissioner to the United Kingdom, Alexander Downer, helped trigger the initial FBI investigation into Mr Trump's links with Russia.
White House deputy press secretary Hogan Gidley said Mr Trump was trying to facilitate access for the Department of Justice (DOJ) to the Australian Government.
"The Democrats clearly don't want the truth to come out anymore as it might hurt them politically, but this call relates to a DOJ inquiry publicly announced months ago to uncover exactly what happened," he said in a statement.
"The DOJ simply requested that the President provide introductions to facilitate that ongoing inquiry, and he did so, that's all."
US media has reported the Trump administration has also asked Britain and Italy to help with the inquiries.
In a letter dated 28 May, 2019, Mr Hockey wrote to Mr Barr to commit Australia to assisting the US Government's efforts to investigate the origins of the FBI probe into Russian links to the 2016 election.
"I note that the President referred to Australia, the United Kingdom and Ukraine as potential stakeholders," Mr Hockey wrote.
"The Australian Government will use its best endeavours to support your efforts in this matter."
Mr Hockey said Australia would provide the US with all relevant information that supported its inquiries.
Mr Trump is facing the prospect of impeachment amid allegations he pressured the Ukrainian President Volodymyr Zelensky to investigate former vice president Joe Biden, a potential Democratic challenger in next year's US elections.
Democrats demand records from president's lawyer
Meanwhile, Democrats have demanded records from the president's personal lawyer, Rudy Giuliani, in the next step of an effort that could remove Mr Trump from office.
Mr Giuliani has admitted to asking Ukraine to investigate corruption allegations - widely debunked - against former vice-president Joe Biden.
Lawmakers issued a subpoena for those communication records from Mr Giuliani.
A phone call between President Trump and the president of Ukraine was flagged by a whistleblower.
A rough transcript emerged last week of that call between Mr Trump and President Volodymyr Zelensky.
The transcript shows the US president urged him to investigate the discredited allegations against Mr Biden, a 2020 Democratic frontrunner, and his son.
The call is now at the centre of an impeachment inquiry by Democrats - an effort that could see Mr Trump expelled from office, but doing so would require members of his Republican party to turn against him.
Three chairmen of key House of Representatives committees - Intelligence, Foreign Affairs and Oversight - sent the subpoena notice to Mr Giuliani on Monday.
The subpoena was expected, as Democrats had earlier said they wanted to question Mr Giuliani, a central figure in the saga.
On the phone call, Mr Trump asked the Ukrainian president to co-ordinate with his lawyer on any inquiry into Mr Biden and son Hunter.
During a 19 September appearance on CNN, Mr Giuliani confirmed he asked Ukraine to "look into the allegations that related to my client, which tangentially involved Joe Biden in a massive bribery scheme".
In their subpoena letter, the chairmen said: "In addition to this stark admission, you stated more recently that you are in possession of evidence - in the form of text messages, phone records, and other communications - indicating that you were not acting alone and that other Trump Administration officials may have been involved in this scheme."
The chairmen have demanded all relevant communications be submitted by 15 October.
Mr Giuliani and the White House have not yet responded to the subpoena, though on Sunday, Mr Giuliani told ABC News he "wouldn't co-operate" with Mr Schiff.
What is the impeachment inquiry about?
An intelligence community whistleblower filed a complaint last month, saying he had an "urgent concern" that Mr Trump had used his office to "solicit interference from a foreign country" in the upcoming 2020 presidential election.
Democrats launched an impeachment inquiry on Tuesday focusing on the call flagged in this complaint, where Mr Trump spoke with the Ukrainian leader about the Biden allegations.
Mr Trump's political rivals have accused him of improperly seeking foreign help to try and smear Mr Biden and using military aid as a bargaining tool.
Ukrainian ex-prosecutor general Yuriy Lutsenko has told the BBC that there was no reason to investigate Mr Biden or his son Hunter Biden, who had worked for a Ukrainian energy firm.
Mr Biden had boasted about getting Ukraine's former prosecutor general Viktor Shokin fired, though he was not the only lawmaker at the time to call for Mr Shokin's removal.
The move was also supported by the EU as an anti-corruption effort.
Congress is currently in recess, but Democrats plan on remaining in Washington over the break to move "expeditiously" on with impeachment proceedings and additional subpoenas.
Ukrainian leader Mr Zelensky told reporters that he is not planning to release Ukraine's transcript of the call with Mr Trump.
"There are certain nuances and things which I think it would be incorrect, even, to publish," Mr Zelensky told Reuters.
Also on Monday, a senior official told the Wall Street Journal that Secretary of State Mike Pompeo was among those who listened in to the 25 July call.
Mr Pompeo has also been subpoenaed for Ukraine-related documents by House Democrats.
- ABC / BBC