Joe Biden wins Arizona for Democratic primary sweep

Joe Biden won the Arizona primary over Bernie Sanders, giving him a sweep of the three US states which voted on Tuesday to choose a Democratic candidate to face President Donald Trump in November.

As the United States grappled with combating the spreading coronavirus pandemic, voters handed the former vice president victory in delegate-rich Florida, as well as Illinois and Arizona.

In Florida, the 77-year-old won 62 per cent to 23 per cent against Sanders, a 78-year-old self-described "democratic socialist" senator from Vermont.

Biden was ahead by 23 percentage points in Illinois, with 89 per cent of precincts reporting.

"Our campaign has had a very good night. We've moved closer to securing the Democratic Party's nomination for president, and we're doing it by building a broad coalition that we need to win in November,"Biden said in televised remarks from his home in Delaware.

Biden now has a commanding lead in the all-important race for the delegates needed to become the nominee.

On Tuesday Biden's delegate count stood at 1,147 compared to Sanders's 861. A candidate needs 1,991 delegates to secure the Democratic nomination and face Trump in the November election.

Biden has long said that Americans want pragmatic results, not the political "revolution" advocated by Sanders.