Joe Biden warned that Donald Trump was "determined to destroy" US democracy, as both the Democratic president and his Republican rival scored big wins in the Super Tuesday primaries and head toward a rematch.

Trump "is determined to destroy our democracy, rip away fundamental freedoms like the ability for women to make their own health care decisions, and pass another round of billions of dollars in tax cuts for the wealthy —-- and he'll do or say anything to put himself in power," Biden said in a statement released by his campaign.