Washington (AFP) - Arizona's most populous county has confirmed that a draft report of a partisan audit of its vote count in the 2020 presidential election declares Joe Biden as the winner.

The report by Cyber Ninjas, a litte known Florida-based cybersecurity company, shows Maricopa County's result in November was correct, the county tweeted late Thursday.

"The #azaudit draft report from Cyber Ninjas confirms the county's canvass of the 2020 General Election was accurate and the candidates certified as the winners did, in fact, win," it wrote.

The conclusion, which is expected to be released publicly on Friday, effectively ends the discredited Republican-led bid to throw out Biden's victory there in favor of former president Donald Trump.

Maricopa County did not publish the draft report and Cyber Ninjas did not immediately respond to an AFP request.

Biden's victory in the key Arizona county was the first by a Democratic presidential nominee in decades.

Trump supporters and organizations who claim he was cheated out of an election win, including some who have also peddled wild conspiracy theories, funded the review to the tune of millions of dollars.

Since his crushing election defeat, Trump has resurfaced to criticize his successor.

In July, at his first campaign-style rally since leaving the White House, he repeated the lie that he won November's election and that Biden prevailed only through fraud.

The firebrand right-winger, who has been booted from social media and was impeached for inciting the deadly January 6 riot at the US Capitol, may yet seek re-election in 2024 but has not announced his plans.