Donald Trump reportedly urged the Australian prime minister to help with a US investigation which may have brought political benefits to the president.
The New York Times reported that Mr Trump used a phone call to urge Scott Morrison, the Australian leader, to help William Barr, the US attorney general, on an investigation he was running.
The investigation was looking into the origins of the Russian election meddling probe, which long hung over the Trump presidency.
Mr Trump has argued the investigation, which looked at links between the Trump campaign and Russia, was launched inappropriately by the Barack Obama administration before the 2016 election.
This newspaper was unable to independently verify the claim. The White House and Australian government did not immediately comment.
It would be the second time Mr Trump has privately urged a world leader to act over an investigation which was likely to politically benefit himself.
Separately, Mr Trump has suggested the Democrat leading the impeachment inquiry should be arrested for treason as he demanded a meeting with the anonymous whistle-blower whose complaint helped uncover the Ukrainian scandal.
Twice in the last 24 hours the US president has said that Adam Schiff, the congressman who as chairman of the House Intelligence Committee is driving forward the probe, may have committed treason as he lashed out at political opponents and the media.