WASHINGTON (Reuters) - U.S. President Barack Obama has commuted the prison terms of 58 non-violent drug offenders, nearly a third of whom were serving life sentences, the White House said on Thursday.

U.S. President Barack Obama delivers the keynote speech at the Asian Pacific American Institute for Congressional Studies' (APAICS) 22nd annual awards dinner at the Washington Hilton hotel in Washington May 4, 2016. REUTERS/James Lawler Duggan

“It just doesn’t make sense to require a non-violent drug offender to serve 20 years, or in some cases, life, in prison,” Obama said in a blog post.

Many of the convicts had been serving time for crack cocaine. Crack users have for years faced far steeper penalties than users of powder cocaine, even though the two substances are molecularly similar. Critics have said the disparity has unfairly hurt poor African-American communities.

Obama has pushed to reform the U.S. criminal justice system to reduce the number of people serving long sentences for such crimes, and it is one of the few issues for which the Democratic president has received support from Republican lawmakers.

His administration announced the most ambitious clemency program in 40 years in April, 2014. The program has struggled under a deluge of unprocessed cases.

Still, the number of commutations Obama has given is more than double those given by the previous six presidents combined, the White House said.

Rachel Barkow, faculty director at the Center on the Administration of Criminal Law at New York University School of Law, said Obama has to speed up his clemency program or the “initiative remains a lottery” for thousands of other convicts.

She called the commutations a step in the right direction and added, “They also illustrate how much more this administration needs to do.”

Obama has now commuted the sentences of 306 people, including 110 who had been serving life terms.

Among those named on Thursday were Jasmine Allen of Florida, who had been convicted of conspiracy to distribute a small amount of cocaine base, Wade Cutchen of Virginia, who was serving a sentence for possession and intent to distribute heroin and cocaine, and Tomma Jean Kent of Iowa, who had been convicted of conspiracy to distribute methamphetamine.