The vast majority of the ballots still being counted are from Maricopa County, the most populous area of the state. The next update from elections officials in Arizona is expected around 3pm NZ time.
The Trump campaign says it is confident the President will overtake Biden when all votes in the state are tallied.
The AP earlier called the race in Arizona for Biden after an analysis of ballots cast statewide concluded Trump could not catch up in the ballots left to be counted - but other networks such as CNN have it still in play
There has been an ongoing fight between the Fox News Decision Desk, which makes the network's calls and has called Arizona for Biden, and the Trump campaign, which insists the President will end up winning the state. The Decision Desk isn't budging.
Increasingly anxious Democrats are keeping their eye on Arizona. You could see those nerves on MSNBC late last night, as left-leaning host Rachel Maddow learned of the state's latest vote totals.
"The suspense has been would this be a Trump-favourable group, or would it be a Biden-favourable group? So we just got those new numbers," analyst Steve Kornacki said of the new data.
"Donald Trump is getting about 59 per cent of these votes."
"Oh god. That's crazy," Maddow replied.
If he takes Arizona, Biden's victories in the Great Lakes states leave him at 264, meaning he was one battleground state away — any would do — from becoming president-elect.
Trump, with 214 electoral votes, faced a much higher hurdle. To reach 270, he needs to claim all four remaining battlegrounds: Pennsylvania, North Carolina, Georgia and Nevada.
Arizona has a long political history of voting Republican. It's the home state of Barry Goldwater, a five-term, conservative senator who was the Republican nominee for president in 1964. John McCain, the party's 2008 presidential nominee, represented the state in Congress from 1983 until his 2018 death.
But changing demographics, including a fast-growing Latino population and a boom of new residents — some fleeing the skyrocketing cost of living in neighbouring California — have made the state friendlier to Democrats.
Many of the gains have been driven by the shifting politics of Maricopa County, which is home to Phoenix and its suburbs. Maricopa County accounts for 60 per cent of the state's vote, and Biden leads there by 4.2 percentage points in votes that have already been tabulated.
AP, additional reporting news.com.au
