Maria Shriver and then Califoria governor Arnold Schwarzenegger walk during Maria Shriver's Women's Conference at the Long Beach Convention Center in October 2010 in Long Beach, Calif. (Getty Images/Frederick M. Brown)

Former California Gov. Arnold Schwarzenegger and his wife of 25 years, Maria Shriver, have announced that they are separating.

The statement, issued by a spokesman for Schwarzenegger on Monday, said the two were working on the future of their relationship while living apart and they would continue to parent their four children together.

"This has been a time of great personal and professional transition for each of us," the two said in a prepared statement. "After a great deal of thought, reflection, discussion, and prayer, we came to this decision together."

It was not clear from the statement if either remained at their estate in Brentwood, or whom the children were with.

Schwarzenegger's spokesman, Daniel Ketchell, said he wouldn't answer questions beyond what was said in Monday's statement.

Schwarzenegger, a Republican, finished his seven-year run as governor in January and has been travelling to deliver speeches and pursuing entertainment projects. He tweeted frequently during his travels to such faraway places as Brazil, Nigeria and France.

Shriver was not mentioned in his Twitter updates from the road.

Shriver, also active on social networks, posted three updates on her Twitter page on the day of their 25th wedding anniversary, April 26, but did not mention the milestone.

About a month before the anniversary, Shriver wrote on her Facebook page that she was going through a transition in her life.

"As you know, transitions are not easy. I'd love to get your advice on how you've handled transitions in your own life," she said in a video posted on YouTube.

"It's so stressful to not know what you're doing next. People ask you what are you doing and then they can't believe that you don't know what you're doing," she said.

Schwarzenegger has said that Shriver, who is keenly attuned to the risks of a life in politics, initially was very upset about his plan to run for governor. But when Schwarzenegger announced his decision on The Tonight Show with Jay Leno in August 2003, he said his wife stood by his decision.

During Schwarzenegger's time as governor, Shriver and the couple's children never moved to Sacramento, preferring their secluded canyon estate a few miles from the Pacific Ocean. Schwarzenegger never settled in Sacramento, choosing instead to commute by private jet between his home and the state capitol.

Shriver, a member of the Kennedy political dynasty and the daughter of the late Eunice Kennedy Shriver, left her job as an NBC News correspondent after Schwarzenegger took office.

In a May 2009 commencement speech at the University of Southern California, Schwarzenegger alluded to the powerful influence Shriver had on his life. He said when people ask him the secret to success, "I say, number one, come to America. Number two, work your butt off. And number three, marry a Kennedy."

As the state's first lady, Shriver ran an annual women's conference that attracted a long list of business, political and entertainment luminaries, along with an audience of thousands. She also was credited with overhauling the California Museum in downtown Sacramento and, with Schwarzenegger, starting the California Hall of Fame.

The separation announcement comes months after the death of Shriver's father, Peace Corps founder and former vice-presidential candidate Sargent Shriver, in January.