Biden slams Trump 'extremist' assault on democracy

US President Joe Biden took fierce aim at Donald Trump and his "extremist" supporters, labelling them enemies of American democracy in a prime-time address that sought to fire up voters ahead of key midterm elections.

Speaking in Philadelphia, the cradle of US democracy, the president launched an extraordinary assault on those Republicans who embrace Trump's "Make America Great Again" ideology -- and urged his own supporters to fight back.

"Donald Trump and the MAGA Republicans represent an extremism that threatens the very foundations of our republic," thundered Biden, speaking near the spot where the Declaration of Independence and the US Constitution were adopted more than two centuries ago.

"They embrace anger. They thrive on chaos. They live not in the light of truth but in the shadow of lies."

"There is no place for political violence in America. Period. None. Ever," warned the 79-year-old Democrat -- in a reference to last year's assault on the US Capitol by hardline Trump supporters refusing to accept his defeat.

Citing the nationwide assault on abortion rights by hardline conservatives -- and fears for other freedoms from contraception to same-sex marriage -- the US leader charged that "MAGA forces" were "determined to take this country backwards."

With control of Congress in the balance come November, Biden appealed directly to mainstream Republicans to join forces with Democrats and repudiate Trump's brand of politics -- which still holds sway over much of his party.