The race for the 2024 Republican White House nomination is about to heat up as two long-tipped contenders enter the fray.

Former US Vice-President Mike Pence and ex-New Jersey Governor Chris Christie have officially joined the increasingly crowded field.

It places a big political target on the back of the current front-runner, former President Donald Trump, setting the stage for what promises to be an acrimonious contest.

The eventual winner looks likely to challenge President Joe Biden, a Democrat, in the election of November next year.