WASHINGTON, Aug 1 (Reuters) - The U.S. Drug Enforcement Administration's acting director criticized President Donald Trump for telling law enforcement officers not to be "too nice" to suspects, urging DEA agents to show "respect and compassion" and saying he felt compelled to speak out when "something is wrong."

Acting Director Chuck Rosenberg sent an agency-wide email on Saturday, one day after Trump's speech to officers in Brentwood, New York, on Long Island. The email was seen by Reuters on Tuesday.

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.

11 PHOTOS Acting DEA Administrator Chuck Rosenberg See Gallery Acting DEA Administrator Chuck Rosenberg Acting Drug Enforcement Administration (DEA) Administrator Chuck Rosenberg speaks about fentanyl at the headquarters of the Drug Enforcement Agency June 6, 2017 in Arlington, Virginia. The news conference addressed the dangers law enforcement and first responders face when encountering fentanyl. / AFP PHOTO / Brendan Smialowski (Photo credit should read BRENDAN SMIALOWSKI/AFP/Getty Images) WASHINGTON, DC - JUNE 07: Acting Drug Enforcement Administrator Chuck Rosenberg testifies before the Senate Judiciary Committee June 7, 2016 in Washington, DC. The committee heard testimony on the topic 'Deadly Synthetic Drugs: The Need to Stay Ahead of the Poison Peddlers.' (Photo by Win McNamee/Getty Images) Deputy Attorney General Sally Q. Yates (L) speaks alongside FBI Director James Comey (2L) and Chuck Rosenberg (C), acting administrator of the Drug Enforcement Administration (DEA)as they attend a new Implicit Bias Training program at the Department of Justice in Washington, DC, June 28, 2016. / AFP / SAUL LOEB (Photo credit should read SAUL LOEB/AFP/Getty Images) Drug Enforcement Administration Acting Administrator Chuck Rosenberg speaks during a press conference at the US Department of Justice in Washington, DC, on July 13, 2017. / AFP PHOTO / JIM WATSON (Photo credit should read JIM WATSON/AFP/Getty Images) UNITED STATES - JUNE 04: U.S. Attorney Chuck Rosenberg, of the Eastern District of Virginia, announces an indictment against U.S. Representative William Jefferson at a news conference at the Department of Justice in Washington, D.C., June 4, 2007. A grand jury in Alexandria issued a 16-count indictment charging Jefferson with money laundering, conspiracy, obstruction of justice and other crimes. (Photo by Chris Kleponis/Bloomberg via Getty Images) Acting Drug Enforcement Administration (DEA) Administrator Chuck Rosenberg speaks about fentanyl at the headquarters of the Drug Enforcement Agency June 6, 2017 in Arlington, Virginia. The news conference addressed the dangers law enforcement and first responders face when encountering fentanyl. / AFP PHOTO / Brendan Smialowski (Photo credit should read BRENDAN SMIALOWSKI/AFP/Getty Images) BETHESDA, MD - JUNE 20: (L-R) Bureau of Alcohol, Tobacco, Firearms and Explosives Acting Director Thomas Brandon, Drug Enforcement Administraiton acting head Chuck Rosenberg, Federal Bureau of Investigation Acting Director Andrew McCabe and U.S. Marshals Acting Director David Harlow listen to U.S. Attorney General Jeff Sessionsn deliver remarks during the National Summit on Crime Reduction and Public Safety with (2nd at the Hyatt Regency hotel June 20, 2017 in Bethesda, Maryland. Attorney General Jeff Sessions has recused himself from the Justice Department's investigation into Russian involvement in the 2016 presidential election, when he served as an advisor to the campaign of President Donlad Trump. (Photo by Chip Somodevilla/Getty Images) WASHINGTON, DC - JULY 13: U.S. Attorney General Jeff Sessions (L) picks up his remarks from the podium as Acting DEA Administrator Chuck Rosenberg (2nd L) and Acting FBI Director Andrew McCabe (R) look on during a news conference to announce significant law enforcement actions July 13, 2017 at the Justice Department in Washington, DC. Attorney General Jeff Sessions held the news conference to announce the 2017 health care fraud takedown. (Photo by Alex Wong/Getty Images) U.S. Deputy Attorney General Rod Rosenstein (L) listens as acting DEA Administrator Chuck Rosenberg (R) speaks during a news conference on the dangers law enforcement and first responders face when encountering fentanyl at DEA Headquarters in Arlington, Virginia, U.S., June 6, 2017. REUTERS/Kevin Lamarque FBI Director James Comey (R) and Chuck Rosenberg, Acting Administrator of the Drug Enforcement Administration, attend a meeting with U.S. Attorney General Jeff Sessions at the Justice Department in Washington, U.S., February 9, 2017. REUTERS/Yuri Gripas U.S. Attorney Chuck Rosenberg (L) is joined by Assistant Attorney General Alice Fisher (R) as they announce the indictment of Rep. William Jefferson (D-LA) on 16 counts of public corruption, including bribery, in Washington, June 4, 2007. Jefferson was indicted on Monday on 16 criminal counts for conspiring to solicit bribes and pay off a Nigerian official, with $90,000 of an intended bribe found hidden in his home freezer wrapped in aluminum foil. REUTERS/Larry Downing (UNITED STATES) Up Next See Gallery Discover More Like This HIDE CAPTION SHOW CAPTION of SEE ALL BACK TO SLIDE

That suggestion drew criticism from many local law enforcement agencies, as well as Rosenberg. "I write because we have an obligation to speak out when something is wrong," the acting DEA chief said in the email.

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

Rosenberg, who was not nominated by Trump but is a holdover from the Obama administration, was the first head of a federal agency to challenge 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.

12 PHOTOS President Trump addresses members of law enforcement See Gallery President Trump addresses members of law enforcement BRENTWOOD, NY - JULY 28: President Donald Trump speaks at Suffolk Community College on July 28, 2017 in Brentwood, New York. Trump, speaking close to where the violent street gang MS-13 has committed a number of murders, urged Congress to dedicate more funding to border enforcement and faster deportations. Trump spoke to an audience that included to law enforcement officers and the family members of crime victims. (Photo by Spencer Platt/Getty Images) BRENTWOOD, NY - JULY 28: President Donald Trump speaks at Suffolk Community College on July 28, 2017 in Brentwood, New York. Trump, speaking close to where the violent street gang MS-13 has committed a number of murders, urged Congress to dedicate more funding to border enforcement and faster deportations. Trump spoke to an audience that included to law enforcement officers and the family members of crime victims. (Photo by Spencer Platt/Getty Images) Police officers applaud as U.S. President Donald Trump delivers remarks about his proposed U.S. government effort against the street gang Mara Salvatrucha, or MS-13, to a gathering of federal, state and local law enforcement officials in Brentwood, New York, U.S. July 28, 2017. REUTERS/Jonathan Ernst U.S. President Donald Trump delivers remarks about his proposed U.S. government effort against the street gang Mara Salvatrucha, or MS-13, to a gathering of federal, state and local law enforcement officials in Brentwood, New York, U.S. July 28, 2017. REUTERS/Jonathan Ernst BRENTWOOD, NY - JULY 28: President Donald Trump speaks at Suffolk Community College on July 28, 2017 in Brentwood, New York. Trump, speaking close to where the violent street gang MS-13 has committed a number of murders, urged Congress to dedicate more funding to border enforcement and faster deportations. Trump spoke to an audience that included to law enforcement officers and the family members of crime victims. (Photo by Spencer Platt/Getty Images) Police officers look on as U.S. President Donald Trump delivers remarks about his proposed U.S. government effort against the street gang Mara Salvatrucha, or MS-13, to a gathering of federal, state and local law enforcement officials in Brentwood, New York, U.S. July 28, 2017. REUTERS/Jonathan Ernst BRENTWOOD, NY - JULY 28: President Donald Trump speaks at Suffolk Community College on July 28, 2017 in Brentwood, New York. Trump, speaking close to where the violent street gang MS-13 has committed a number of murders, urged Congress to dedicate more funding to border enforcement and faster deportations. Trump spoke to an audience that included to law enforcement officers and the family members of crime victims. (Photo by Spencer Platt/Getty Images) US President Donald Trump delivers remarks on law enforcement at Suffolk Community College in Ronkonkoma, New York July 28, 2017. / AFP PHOTO / Nicholas Kamm (Photo credit should read NICHOLAS KAMM/AFP/Getty Images) Police officers look on as U.S. President Donald Trump delivers remarks about his proposed U.S. government effort against the street gang Mara Salvatrucha, or MS-13, to a gathering of federal, state and local law enforcement officials in Brentwood, New York, U.S. July 28, 2017. REUTERS/Jonathan Ernst Police officers applaud a line by U.S. President Donald Trump as he delivers remarks about his proposed U.S. government effort against the street gang Mara Salvatrucha, or MS-13, to a gathering of federal, state and local law enforcement officials at the Long Island University campus in Brentwood, New York, U.S. July 28, 2017. REUTERS/Jonathan Ernst Police officers look on as U.S. President Donald Trump delivers remarks about his proposed U.S. government effort against the street gang Mara Salvatrucha, or MS-13, to a gathering of federal, state and local law enforcement officials in Brentwood, New York, U.S. July 28, 2017. REUTERS/Jonathan Ernst U.S. President Donald Trump delivers remarks about his proposed U.S. government effort against the street gang Mara Salvatrucha, or MS-13, to a gathering of federal, state and local law enforcement officials in Brentwood, New York, U.S. July 28, 2017. REUTERS/Jonathan Ernst Up Next See Gallery Discover More Like This HIDE CAPTION SHOW CAPTION of SEE ALL BACK TO SLIDE

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. Chuck Canterbury, national president of the Fraternal Order of Police, the nation's largest police union, said 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," Canterbury said in a statement on Saturday.

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

(Reporting by Julia Edwards Ainsley; Editing by Jonathan Oatis)