The result of the US presidential election is hanging on the vote count in a handful of key states, with the race too close to call so far.

By 11pm PST on Wednesday, Democrat Joe Biden currently holds 238 electoral votes — including Arizona, which the Donald Trump team says could change — compared to 213 for the Republican president.

In order to win, 270 electoral votes are needed. Those votes are divided up proportionately among the states.

Much of the delay has resulted from a flood of mailed-in ballots due to the coronavirus — and those types of votes tend to favour Democrats.

If Biden's lead in Arizona holds and he wins Nevada as expected, he could claim victory by taking two of the following three that remain undecided: Wisconsin, Michigan and Pennsylvania.

Should Trump hold North Carolina and Georgia but lose Arizona, he will likely also need to take two out of three in Wisconsin, Michigan and Pennsylvania.

The paths to victory become more murky should some of the expected outcomes change.

Here is a summary of the situation:

Pennsylvania

Perhaps the state that could take the longest to declare a winner — and one that could potentially decide the outcome with 20 electoral votes at stake.

With 79 per cent of the vote counted in the industrial Rust Belt state, Trump was ahead with 53.9pc compared to Biden's 44.8.

Remaining ballots are however expected to favour Biden, who was born in the state.

Much to Trump's chagrin, the state has decided to allow mailed ballots sent by election day but received up to three days afterward to be counted due to coronavirus complications.

North Carolina

Trump appeared favoured to win North Carolina's 15 electoral votes despite a strong showing by Biden, but it remained too close to call.

With 95pc counted in the southeastern state, Trump had 50.1pc and Biden 48.6.

Mail ballots sent on or before election day can be counted until November 12.

Michigan

Trump narrowly won Michigan over Hillary Clinton in 2016 along with the Midwestern industrial state's 16 electoral votes, but it is now too close to call.

Biden was slightly ahead with 49.5pc to 48.9pc with 92pc of the ballots counted.

Remaining votes to count have been expected to favour Biden.

State officials have signalled that a winner could become clear on Wednesday even if it is not a final result.

Wisconsin

Another Trump win in 2016 whose 10 electoral votes could flip to Biden.

With 97pc counted in the Midwestern state known for its dairy farms, Biden had 49.5pc compared to Trump's 48.8.

A final result is expected on Wednesday.

Nevada

Biden had been expected to win Nevada's six electoral votes, but the western state that is home to gambling hub Las Vegas remains too close to call.

With 86pc counted, Biden had 49.3pc to 48.7 for Trump.

State officials said on Wednesday that further results would not be known until Thursday.

Georgia

Biden performed unexpectedly well in the southeastern state that is traditionally a Republican stronghold, but Trump was still narrowly ahead. The state has 16 electoral votes.

With 92pc counted, Trump had 50.5pc compared to 48.3 for Biden.

A final result is expected on Wednesday.