He announced on Sunday - the anniversary of his pardon by President Donald Trump - that he will see re-election to his old job next year.

Arpaio, 87, a Republican who was voted out of office in 2016 after a 24-year tenure as Maricopa County's longest-serving sheriff, said he will seek his party's nomination for the post again in the August 4, 2020 primary, running against his onetime chief deputy, Gerard Sheridan.

The winner of that primary will likely face the man who defeated Arpaio in 2016, the current incumbent sheriff, Democrat Paul Penzone, in the November 2020 general election.

Arpaio lost a Republican primary bid in 2018 for the US Senate seat in Arizona vacated by the retirement of fellow Republican Jeff Flake, a frequent critic of Trump.

During his stint as the top elected lawman in Arizona's largest county, Arpaio branded himself as "America's Toughest Sheriff" as he oversaw roundups of suspected illegal immigrants, reinstituted chain gangs, erected tent cities to house prisoners and forced inmates to wear pink.

But a federal judge cited him for criminal contempt in 2017, ruling that Arpaio had defied a 2011 court order barring his deputies from detaining Latinos solely on the suspicion that they were in the country illegally.

But Trump, who had carried Arizona by five percentage points in his 2016 presidential election, pardoned Arpaio on August 25, 2017, before he could be sentenced.

Still, the former sheriff ended up with less than 20 per cent of the vote.

Announcing his latest bid for office, Arpaio vowed if re-elected to bring back his tent-city and other "popular jail policies", as well as to return his controversial volunteer "posse" to its former strength.

Australian Associated Press