By Timothy Gardner

WASHINGTON (Reuters) - President Barack Obama on Friday shortened the prison sentences of 72 convicts serving time for non-violent drug offenses in the latest round of commutations, the White House said.

The commutations are part of Obama's effort to reform the U.S. criminal justice system. He has so far shortened the sentences of 944 convicts, including those of 324 who were serving life terms.

"Our nation is a nation of second chances, where mistakes from the past will not deprive deserving individuals of the opportunity to rejoin society and contribute to their families and communities," White House counsel Neil Eggleston said in a statement about Obama's commutation push. The president will continue to grant commutations until he leaves office on Jan. 20, Eggleston has said.

Marijuana reform activists have urged the Obama administration to legalize pot, which is on a list of the most dangerous drugs such as heroin. But in August it declined to do so, only relaxing certain restrictions on growing pot for medical research.

The administration has instead focused on the commutation program Obama launched in 2014, the country's most ambitious in 40 years.

Many of the convicts have been serving terms on crack cocaine offenses. Crack offenders have for years faced stiffer penalties than offenders of powder cocaine, even though the two substances are molecularly similar. Critics have said that disparity has unfairly hurt minority communities.

All 944 convicts were required to go through curriculums such as getting the equivalency of a high school degree, vocational programs, or substance abuse programs designed to prepare them to reenter society.

Convicts with shortened terms include Ricky Mitchell of Waycross, Georgia who was serving a life term since 1997 for crack cocaine and other offenses. Mitchell will now be released in 2027, conditioned on enrollment in a drug treatment program.

Lasalle Boone of Portsmouth, Virginia was serving a 12-year term for possession with intent to distribute base cocaine that had been set to expire in 2020. Boone's sentence was commuted to expire in 2017.

Obama and a group of bipartisan lawmakers this year had tried to push though legislation to institute broad criminal justice reforms, but the effort stalled ahead of the Nov. 8 election. Eggleston urged Congress to act on the bill after it returns from a long recess this month.

(Reporting by Timothy Gardner; Editing by James Dalgleish)