The king, as in Larry King, is stepping aside.

In an internal memo sent late Tuesday, CNN President Jonathan Klein informed staffers that the long-time talk show host would announce his decision to descend his primetime throne on his broadcast Tuesday at the top of his show.

“After 25 years,” the memo said, “Larry has decided to take a step back from the nightly grind. He wants to take some time for himself and his family. So he will end his run with ‘Larry King Live’ on his own terms, sometime this fall.”

The memo pointed out that King is not leaving CNN. “Larry is a beloved member of the CNN family and he will continue to contribute to our air with periodic specials,” Klein said.

There had been speculation that King would be leaving for the past several months, with “Britain’s Got Talent” judge Piers Morgan rumored to be one possible replacement. CNN said it would announce plans for the 9 p.m. hour in the weeks ahead.

On his Tuesday program, Diane Sawyer and Regis Philbin were among the callers who sung his praises. King, whose contract was due to expire in June 2011, told guest Bill Maher, “I want to do other things that I haven’t been able to do.”

The announcement comes as CNN finds itself battling Fox News Channel and MSNBC in the cable news wars. As audiences have gravitated toward politically pointed, opinion-led shows and newsmakers themselves have discovered many more outlets for interviews, King’s hour-long talkathon slipped behind Fox’s Sean Hannity and MSNBC’s Rachel Maddow in the ratings.

In May, King hit a 20-year low by averaging 725,000 viewers in the 9 p.m. hour, according to Nielsen. His ratings have rebounded in June.

CNN’s entire primetime schedule has been lagging badly in the ratings for some time, and Klein has been busy making changes. With 8 p.m. anchor Campbell Brown announcing her departure from CNN last month, he announced last week that the pair of Eliot Spitzer and Kathleen Parker would take her place, utilizing a format akin to CNN’s “Crossfire.” Another new show was added at 7 p.m. earlier this year featuring CNN correspondent John King, but that has yet to find traction with viewers.

More recently, the 76-year-old broadcast veteran made viewers and pundit ponder aloud if he was disconnected during interviews with politicians and with celebrities. A session with Lady Gaga last week suggested he was not fully prepared for the pop icon.

King said he began thinking about stepping down as his 25th anniversary week ended earlier this month, after he interviewed LeBron James, Bill Gates, President Barack Obama, and Lady Gaga. He’s conducted some 50,000 interviews during a 53-year broadcasting career.

Guessing King’s successor has been a parlor game in media circles for years, and King himself has mentioned Ryan Seacrest and Keith Olbermann as worthy replacements. Katie Couric is another name that has been bandied about more recently, but recent reports have suggested she is intent on renewing her CBS deal.

In recent months, King’s marriage to Shawn Southwick, 50, has run into trouble. In April, the pair said they would be divorcing, but about a month later, the two decided to reunite and work on their problems.

In June, Southwick attempted suicide at her home in Utah by overdosing on prescription drugs, according to a police report detailing the incident. King and Southwick, who were married in 1997, have two young sons, Chance and Cannon. King has been married eight times, previously. He married one of his wives, twice.

“It’s time to hang up my nightly suspenders,” King added in a message sent to fans via Twitter late Tuesday.