US President Donald Trump has come under fire from within the Republican Party over his decision to pardon a former Arizona sheriff convicted of criminal contempt in a racial profiling case.

Key points: Paul Ryan reiterated that police must "respect the rights of everyone"

Paul Ryan reiterated that police must "respect the rights of everyone" Joe Arpaio was convicted for ignoring a court order barring officers from racially profiling motorists

Joe Arpaio was convicted for ignoring a court order barring officers from racially profiling motorists Latino motorists were targeted on the suspicion they were illegal immigrants

Mr Trump yesterday announced he was pardoning Joe Arpaio, an anti-immigration hardliner found guilty last month for flouting a 2011 court order that barred officers from detaining Latino motorists solely on the suspicion they were illegal immigrants.

The Republican speaker of the House of Representatives, Paul Ryan, was one of a handful of prominent Republicans who opposed the pardon.

"Law enforcement officials have a special responsibility to respect the rights of everyone in the United States," Mr Ryan's spokesman, Doug Andres, said in a statement.

"We should not allow anyone to believe that responsibility is diminished by this pardon.

"The speaker does not agree with the decision."

Arizona senator John McCain and former Florida governor Jeb Bush have also criticised Mr Trump for the controversial pardon.

"The President has the authority to make this pardon, but doing so at this time undermines his claim for the respect of rule of law as Mr Arpaio has shown no remorse for his actions," Mr McCain said in a statement.

Mr Arpaio, 85, was an outspoken supporter of Mr Trump's presidential campaign and both men have argued for tougher policies against illegal immigration.

As President, Mr Trump has broad powers to issue pardons and he had said Mr Arpaio was convicted for "doing his job".

Mr Trump had telegraphed his intention to pardon Mr Arpaio for days. ( Reuters: Rick Scuteri, file photo )

Known as "America's toughest sheriff", Mr Arpaio admitted to inadvertently disobeying the court order, but said his behaviour did not meet a criminal standard.

He has previously attracted controversy for setting up an outdoor jail called Tent City, where inmates were housed in military-style tents which would heat up to temperatures as high as 63 degrees Celsius.

Mr Arpaio lost his bid for re-election in Arizona's Maricopa County in November, after 24 years in office.

Trump reportedly asked Sessions to drop case

The Washington Post reported on Saturday that Mr Trump had asked Attorney-General Jeff Sessions last spring whether it would be possible for the government to drop the criminal case against Mr Arpaio.

After being advised that would be inappropriate, Mr Trump decided to let the case go to trial and, if Mr Arpaio were convicted, to grant clemency later, the Post reported.

Arizona's current sheriff says Tent City will be closed later this year. ( AP: Ross D Franklin, file image )

The newspaper said its sources, who were not identified, were three people with knowledge of the conversation.

"It's only natural the President would have a discussion with administration lawyers about legal matters. This case would be no different," White House press secretary Sarah Huckabee Sanders told the newspaper.

Mr Trump had telegraphed his move for days, but the pardon was unusual given that Mr Arpaio is awaiting sentencing.

A racially charged choice While many legal experts believed a prison sentence was unlikely, Joe Arpaio's conviction was viewed as an outrage by Donald Trump's base. They saw him as one of the few cops prepared to enforce immigration laws in the states. The racially charged pardon has outraged civil liberties and ethics lawyers already furious over the President's response to the deadly violence in Charlottesville. They say it will send a message to police that the law doesn't apply to them. Mr Arpaio has thanked the President for his decision but shifting demographics in Phoenix meant the sheriff had already been voted out. The war over chain gangs, prison tents and pink underwear had been lost but he'll be front and centre in a bigger battle looming over race and immigration. - Analysis by North America correspondent Conor Duffy

It also had not gone through the normal pardon process, which includes lengthy reviews by the Justice Department and the White House counsel's office.

Jens David Ohlin, vice dean and professor at Cornell Law School, told the Associated Press he was disturbed by the pardon given Mr Trump's relationship with the judiciary throughout both his campaign and early administration.

"[Mr Trump] hasn't shown much respect for either members of the judiciary or the proper role of the judiciary within our constitutional structure," Mr Ohlin said.

During the campaign, Mr Trump called Chief Justice John Roberts "an absolute disaster" and "disgraceful," mainly for two opinions Mr Roberts wrote that left president Barack Obama's health care law intact.

He also went after US District Judge Gonzalo Curiel, who presided over fraud lawsuits against Trump University — Mr Trump said Mr Curiel couldn't be fair because of his "Mexican heritage", in reference to his campaign pledge to build a wall on the US-Mexico border.

Reuters/AP