California Governor Gavin Newsom will impose on Wednesday a moratorium on state executions and a temporary reprieve for all 737 inmates on death row in the state, the media reported.
According to the Washington Post, Newsom will sign an executive order later in the day, describing the death penalty as "inconsistent with our bedrock values".
California has not carried out any executions since 2006, as a series of court battles over execution methods have been waged. The order will give a reprieve from execution - though not release - to California's 737 death row inmates, about a quarter of the nation's population awaiting capital punishment.
It will also annual California's lethal injection protocol and close the execution chamber at San Quentin State Prison, where the state's most notorious criminals have been put to death.
The Governor took office in January and a death penalty moratorium was one of his campaign pledges.
"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," he said in a statement issued with the executive order.
"In short, the death penalty is inconsistent with our bedrock values and strikes at the very heart of what it means to be a Californian."
Two voter initiatives to end the death penalty in California narrowly failed to gain a majority in recent years, with 48 per cent support in 2012 and 47 per cent support in 2016. Governor Newsom supported both initiatives.
But a separate proposition voted on in 2016 won support for its demand to speed up executions in California.
The Governor does not have the power to abolish the state's 1978 death penalty legislation permanently. A repeal would require a popular vote in favour of the change. The next opportunity for such a ballot would be at the 2020 elections.
The reprieves Governor Newsom issues now will expire when he leaves office. His current term lasts until January 2023.
More than 900 people have been sentenced to death in California since 1978, but only 13 have been executed. Another 79 died of natural causes and a further 26 took their own lives, according to figures from the California Department of Corrections and Rehabilitation.
The death penalty is a legal punishment in 30 US states. Since 1976, Texas carried out the most executions (560), followed by Virginia (113) and Oklahoma (112). There are 2,738 inmates on death row in the US.