WASHINGTON -- The head of the Drug Enforcement Administration is refusing to support a bill backed by the Obama administration that would lower the length of mandatory minimum sentences for federal drug crimes, putting her at odds with her boss Attorney General Eric Holder on one of the criminal justice reform initiatives he hopes to make a centerpiece of his legacy.

During testimony before the Senate Judiciary Committee last week, Sen. Chuck Grassley (R-Iowa) asked DEA Administrator Michele Leonhart about the role of mandatory minimums in drug cases. Grassley cited the opposition among some law enforcement groups to the Smarter Sentencing Act, a bipartisan bill that would reduce the length of mandatory minimum sentences for some drug crimes.

"Having been in law enforcement as an agent for 33 years, [and] a Baltimore City police officer before that, I can tell you that for me and for the agents that work for DEA, mandatory minimums have been very important to our investigations," Leonhart said. "We depend on those as a way to ensure that the right sentences are going to the ... level of violator we are going after."

The Huffington Post asked a DEA spokeswoman on Monday whether, given Leonhart's remarks, the DEA administrator supported the position of the Obama administration on the Smarter Sentencing Act.

"We will not be adding anything to Administrator Leonhart's on-the-record comment about mandatory minimum sentences before the Senate Judiciary Committee last week," the spokeswoman, Barbara Carreno, said in an email.

Leonhart's comment last week, Carreno said, "will have to speak for itself."

Leonhart was originally confirmed as deputy administrator of the DEA during the Bush administration in 2004, but was nominated to take over the agency by President Barack Obama over the objections of many drug policy reformers. She has been at the DEA since 1980.

Leonhart has already reportedly slammed the president behind closed doors for comparing weed to alcohol, and has said that the legalization of marijuana in Washington and Colorado -- which the Obama administration allowed to move forward -- has only made DEA agents "fight harder ." She's also suggested that gangs are taking over in Washington and Colorado in the wake of marijuana legalization, even as Holder has said he's "cautiously optimistic " about how things are going in those states.

In 2012, while testifying before the House Judiciary Subcommittee on Crime, Terrorism and Homeland Security, Leonhart refused to acknowledge that marijuana poses fewer health risks than heroin or crack .

Nobody really expected that a lifetime drug warrior would quietly accept marijuana legalization. But publicly undermining the Obama administration's policy position on reforming mandatory minimum drug sentences, especially given that it is a crucial part of Attorney General Eric Holder's Smart on Crime initiative, might be seen differently within the Justice Department and the White House.

Meanwhile, FBI Director Jim Comey, a Republican who served as deputy attorney general during the Bush administration, said he does not believe that the Smarter Sentencing Act would have an impact on the FBI's operations.

"Wherever I go, I ask my folks, 'Do you see our work being impacted, potentially impacted?' And the answer I hear is no," Comey said in response to a question from The Huffington Post during a meeting with reporters on Friday. "Given the nature of the work we tend to do, it's in the main not impacted by that change in policy."

Comey said the FBI would keep an eye on the legislation.

"I know from my experience ... that the mandatory minimums are an important tool in developing cooperators," Comey said.