Vote counting in the US presidential election is due to begin in the next few hours in some states.

Eligible voters are casting their ballots on Tuesday. Indiana and Kentucky will be the first to start counting votes at 6 p.m. local time.

A research group at the University of Florida says more than 82 million people had voted by Monday via mail-in and at polling stations.

Democratic candidate Kamala Harris and Republican nominee Donald Trump fought a very tight race until the final stage, with the economy, immigration and foreign policy key points of contention.

Harris is aiming to become the country's first female president, while Trump is hoping to return to the White House after losing his re-election bid four years ago.

The election is drawing the world's attention because the outcome could affect US foreign policy, including toward the Middle East, Ukraine, and an increasingly assertive China.