'America’s comeback starts right now': Donald Trump launches White House bid

(Andrew Harnik, File/AP)

Former US president Donald Trump has said he will officially mount a third campaign for the White House, launching an early start to the 2024 contest.

The announcement comes just a week after an underwhelming midterm showing for Republicans and will force the party to decide whether to embrace a candidate whose refusal to accept defeat in 2020 pushed American democracy to the brink.