At Long Beach City College, Gov. Gavin Newsom is surrounded by several California mayors after having a meeting with them to discuss affordable housing on Tuesday, Feb. 19, 2019. (Photo by Scott Varley/MediaNews Group/Daily Breeze via Getty Images)

California Governor Gavin Newsom will impose a moratorium on the state's death penalty on Wednesday, granting reprieves to all 737 inmates on death row and closing the state's execution chamber, an administration source said.

Newsom, who Tuesday night hinted at a "major policy announcement," plans to sign an executive order setting the changes in place on Wednesday morning at the state capitol, the source said. No death row inmates will be released, said the source, who declined to be identified.

California's death row is crowded with inmates, many of whom have been there for decades. Newsom is expected to say on Wednesday that he believes capital punishment to be costly and burdensome, and unevenly meted out to minorities and offenders with disabilities, the administration source said.

"I do not believe that a civilized society can claim to be a leader in the world as long as its government continues to sanction the premeditated and discriminatory execution of its people," Newsom plans to say on Wednesday, in remarks seen by Reuters.

His order will withdraw California's lethal injection protocol, which has been challenged in court. It will not affect inmates' convictions or their imprisonment, other than eliminating their death sentences, the source said.