The US Drug Enforcement Administration's (DEA) acting director has criticised President Donald Trump for telling law enforcement officers not to be "too nice" to suspects, saying he felt compelled to speak out when "something is wrong".

Key points: The DEA chief is the first head of a federal agency to challenge Mr Trump's remarks

The DEA chief is the first head of a federal agency to challenge Mr Trump's remarks Mr Trump suggests that offers do away with suspects' rights during arrests

Mr Trump suggests that offers do away with suspects' rights during arrests Incidents of police brutality and killings have created deep divisions in the US

Acting director Chuck Rosenberg on Saturday sent an agency-wide email — seen by journalists on Tuesday — urging DEA agents to show "respect and compassion", one day after Mr Trump's speech to officers in Brentwood, New York, on Long Island.

In his speech, Mr Trump suggested to officers that, as part of a tougher approach to suspects, they do away with practices like protecting the head of a suspect being put into a patrol car.

That suggestion drew criticism from many local law enforcement agencies, as well as Mr Rosenberg.

"I write because we have an obligation to speak out when something is wrong," he wrote.

"The President, in remarks delivered yesterday in New York, condoned police misconduct regarding the treatment of individuals placed under arrest by law enforcement."

Mr Rosenberg, who was not nominated by Mr Trump but is a holdover from the Obama administration, was the first head of a federal agency to challenge Mr Trump's remarks in a wide arena.

Incidents of police brutality and law enforcement killings of black suspects have sparked mass protests nationwide and led many departments to purchase body cameras to record interactions between officers and the public.

President Trump, a Republican, campaigned on a pro-law enforcement platform, winning the support of several police unions by promising to be tough on crime and more supportive of police than his predecessor, Democratic president Barack Obama.

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Chuck Canterbury, national president of the Fraternal Order of Police, the nation's largest police union, said Mr Trump's "off the cuff comments" are taken "too literally" by news media.

"The President knows, just as every cop out there knows, that our society does not, and should not, tolerate the mistreatment or prejudgment of any individual at any point in the criminal justice process," Mr Canterbury said.

The DEA combats drug trafficking into the United States from offices nationwide and several international posts.

Mr Rosenberg said he was not seeking to advance a political agenda, but to remind his agents of their core values, including accountability, diversity and integrity.

"This is how we conduct ourselves. This is how we treat those whom we encounter in our work: victims, witnesses, subjects and defendants. This is who we are," he wrote.

Reuters