US President-elect Joe Biden has moved a step closer to formal election victory, with Arizona officials certified the vote in the state.

They formalised Mr Biden’s narrow victory over Donald Trump on Monday (local time), even as Mr Trump’s lawyers continued to repeat baseless claims of fraud about the vote count in Arizona.

Michigan, Pennsylvania and Georgia have all certified Mr Biden as the winner of the presidential vote in recent days.

Wisconsin – the last remaining key battleground state to formally declare a winner in the November 3 election – followed suit on Monday, after a partial recount that only added to Mr Biden’s 20,600-vote margin over Mr Trump.

President-elect Joe Biden with John Kerry, who will become the US’s international climate envoy. Photo: AAP

Mr Trump has promised to file a lawsuit seeking to undo the Wisconsin results. Elsewhere, he and his legal team continue to attack officials in the key battleground states and lob baseless allegations about a rigged election.

Arizona’s Democratic Secretary of State Katie Hobbs and Republican Governor Doug Ducey both vouched for the integrity of the election before signing off on the results.

“We do elections well here in Arizona. The system is strong,” Mr Ducey said.

He did not directly address Mr Trump’s claims of irregularities but said the state pulled off a successful election with a mix of in-person and mail voting despite the pandemic.

Mr Biden is only the second Democrat in 70 years to win Arizona. In the final tally, he beat Mr Trump by 10,457 votes, or 0.3 per cent of nearly 3.4 million ballots cast.

Eleven Democratic electors will meet on December 14 to formally cast Arizona’s electoral votes for Biden.

Even as Ms Hobbs, Mr Ducey, Arizona’s attorney-general and chief justice of the state Supreme Court certified the election results, Trump lawyers Rudy Giuliani and Jenna Ellis met in a Phoenix hotel just a few kilometres away to lay out claims of irregularities in the vote count in Arizona and elsewhere. They provided no evidence of widespread fraud.

Mr Giuliani, who is leading Mr Trump’s legal fight, held a similar event in Pennsylvania last week with state Republicans at which they claimed the presidential election was corrupt.

But election challenges brought by the Trump campaign and his backers in key battleground states have largely been unsuccessful. Despite that, Mr Trump continues to allege voter fraud while refusing to concede he lost the election.

According to the Associated Press, there is no evidence of widespread fraud in the 2020 US election. In fact, election officials from both political parties have stated publicly that the election went well and international observers confirmed no serious irregularities.

-with AAP