Nervous federal prosecutors attempted to rally opposition Friday to criminal sentencing reform in response to President Barack Obama’s week of issuing commutations and making pro-reform speeches.

The president and a bipartisan alliance in Congress say inflexible penalties for various drug crimes should be reduced or eliminated as a matter of fairness. But the National Association of Assistant U.S. Attorneys says elected officials should make no such change.

Obama, who on Thursday became the first sitting president to visit a federal prison, would threaten public safety if he signs legislation allowing judges greater discretion, they warned.

“The federal criminal justice system is not broken,” Steve Cook, the association's president, said at a lightly attended event in the nation's capital. “What a huge mistake it would be,” he said, to change sentencing laws.

Cook predicted the crime rate would rise and prosecutors would lose a tool to extract information if laws were made more lenient. He also denounced reform proponents for saying nonviolent offenders are being ensnared by tough decades-old drug laws.

“They have misled the public every time they say, 'We’re talking about nonviolent drug offenders,'” he said. “Drug trafficking is inherently violent. … If you’re not willing to engage in violence [then] you will be out of the business quickly, or worse.”

Cook said the small number of inmates whose sentences have been shortened by Obama – the president has issued 76 drug crime commutations total, 46 of them this week – shows there’s not much of a problem with people serving unreasonably long sentences.

Rather than focus on reducing sentences, he said, the government should consider building more prison facilities. “Do I think it would be a good investment to build more [prisons]? Yeah, no question about it!” he said.

The U.S. has the highest number of prisoners in the world at about 2 million, most of whom are held in state or local facilities. More than 200,000 are held in federal prisons.

Molly Gill, government affairs counsel at the advocacy group Families Against Mandatory Minimums, says Cook’s assertion the crime rate would rise after sentencing reform is a “demonstrably false claim and a shameful scare tactic.” In Michigan, New York and other states, she says, crime rates did not spike after mandatory minimums were repealed.

Gill also disputes that drug trafficking is inherently tied to violence, and says she is backed up by inmate profiles on FAMM’s website.

Government statistics, she points out, additionally show just 16 percent of federal drug convictions in fiscal year 2014 involved a weapon and only 142 of 20,757 drug cases that year – less than 1 percent – featured violence or threats of violence from the defendant.

Prosecutors and judges, of course, aren’t uniformly against sentencing reform.

In June, 130 former prosecutors, judges and law enforcement officials signed a letter asking Congress to allow greater discretion in sentencing.

One retired federal judge, Paul Cassell, told ABC News in February the inflexibility of a sentence he handed down still haunts him: the 55 years without parole he gave to young father Weldon Angelos, who in his 20s and more than a decade ago was convicted of selling marijuana while possessing a gun.

“I sometimes drive near the prison where he’s held, and I think, ‘Gosh, he shouldn’t be there. Certainly not as long as I had to send him there,'” Cassell said. “That wasn’t the right thing to do. The system forced me to do it.”

Cook, who was joined by two other federal prosecutors, made much of his speech Friday about societal ills associated with drug addiction, from babies going through withdrawal to people stealing from their families and dying from overdoses and car accidents.

“There’s a pyramid of individuals who are affected by [drug dealers],” he said. “Many view [drug trafficking] as more serious than murder.”

He declined to say if state-legal recreational marijuana businesses and regulators in Colorado and Washington state should face marijuana-related mandatory minimums for breaking federal law.

Cook’s colleagues did not speak at the news conference. He described the event as the first of its kind by the group, which claims to represent 1,500 assistant U.S. attorneys, about 30 percent of the total.