Rick Squarejaw is heading to the Land of Pursuing Opportunities Elsewhere and Miles O'Brien will replace him as co-anchor of CNN's ayem show "American Morning," joining Soledad O'Brien for a three-hour, all-O'Brien weekday block on the cable news network.

Squarejaw, aka Bill Hemmer, is bowing out of the network he's called home for a decade on June 17. He does so after turning down the opportunity to become CNN's senior White House correspondent.

Jack Cafferty, resident Angry Old White Man, also is leaving "American Morning."

He's being shipped over to CNN's new 3 p.m. show, where he will join Happy, Dopey and Grumpy -- otherwise known as former "Crossfire" banterers Paul Begala, James Carville and Robert Novak -- along with a slew of political analysts, a former terrorism adviser to President George W., a former defense secretary, a former Homeland Security inspector general, an ex-acting director of the CIA and a sprinkling of generals, for a fun-filled three hours anchored by Wolf "Look, the Paint -- It's Drying!" Blitzer.

Hemmer's keeping a low profile, which is understandable given that his contract runs a few more months but CNN has given him the go-ahead to talk to other news outlets about possible employment.

So yesterday all he had to say about the change was the following statement: "I have enjoyed working with CNN for the past 10 years and the opportunity to report on countless historical moments has been wonderful. However, at this point in my career, it's time for me to move forward with a new set of challenges."

In mid-May, when reports of the possible anchor switch hit the Internet, Hemmer was much more chatty, telling The Post's Howard Kurtz, "So CNN leaked word; that's the tactic they've chosen" and adding, "It's no secret that other outlets have expressed interest in me" and "CNN has offered me a position at the White House, a good position by many estimations, but I am weighing my options. . . . What does CNN have for me to continue doing there?"

Yesterday, CNN/U.S. President Jonathan Klein insisted the network did not leak the report.

"We would never have done that. We denigrate that as a tactic," he said, adding, "Certainly in this case it wouldn't have served any purpose."

The decision to replace Hemmer with O'Brien -- Miles that is -- was one of "chemistry," Klein explained.

O'Brien's got it; Hemmer, it seems, did not.

"What's vital in the morning is chemistry between anchors," Klein told The TV Column. "Watching Miles handle 'Live From,' where he was paired with a smart, vibrant, fun, female anchor" -- Kyra Phillips -- "and seeing how generous he was in sharing the spotlight and supporting and helping the co-anchor to shine; to me he's the perfect complement to Soledad, who is smart, vibrant, fun . . . and the mother of four."

On the decision to move Cafferty, Klein said they were going to surround Blitzer "with a lot of bright bulbs who have something to say and know how to say it." Blitzer will play the part of "sober center of gravity in the midst of a rollicking situation room."

Which brings us around nicely to the name of Blitzer's new on-air empire, "The Situation Room."

Not be confused with MSNBC's new 9 p.m. show "The Situation," debuting June 13 and anchored by Tucker Carlson -- who, ironically, used to be "Crossfire's" Bashful and, had he not bolted for MSNBC, might have also wound up on "The Situation Room."

"We came up with the idea first," Klein joked, though he noted MSNBC is getting its "Situation" on the air first.

"The Situation Room" will not debut until "mid-summer," CNN said.

It replaces "Inside Politics," "Crossfire" and "Wolf Blitzer Reports" on the CNN lineup.

"The Situation Room," Klein said in a memo to staffers yesterday, "will be modeled in spirit after the White House Situation Room."

For his June 20 debut on "American Morning," O'Brien -- Miles, that is -- is moving from Atlanta to New York City. He told The TV Column that he's already gotten his kids into schools in New York, "which was a tough hurdle," and they're now "doing the real estate thing," which he called "sobering." He cheerfully predicted he and his family will "wind up living in a refrigerator box under the George Washington Bridge.

"The car service will come pick me up there."

In other CNN news, the network has hired two executive producers, for its Anderson Cooper- and Paula Zahn-anchored evening shows.

Victor Neufeld will take on Zahn. His resume includes executive-producing CBS's "Early Show" and a stint as senior exec producer of ABC's newsmags, after executive-producing "20/20."

David Doss, who worked five years as executive producer of "NBC Nightly News" before executive-producing ABC's "Primetime Thursday," will wrangle Cooper.

"David and Victor have proven time and again the ability to take established shows that are good and make them great," Klein told The TV Column yesterday.

"Victor did it with '20/20' when that show was already 13 years old. David did the same in turning 'Nightly News' . . . to a dominant first."

And both men, Klein said, are known for "quality -- they did not rely on cheap tricks; they hunker down and do great journalism."

In other news news, "NBC Nightly News" executive producer Steve Capus has been upped to senior vice president of NBC News.

His No. 2 guy on "Nightly," John Reiss, has been named executive producer of the evening newscast.

Both announcements were made yesterday by NBC News President Neal Shapiro, who has been the subject of recent news reports that he might be working on his own exit strategy.

Capus succeeds Bill Wheatley, who announced his retirement in April.

Capus will be in charge of the evening newscast and will oversee the division's newsgathering and breaking news; he will be arbiter of issues involving ethics, style, standards, safety and other matters affecting the news division's journalistic bearing, NBC News said in its announcement.

Bill Hemmer: "What does CNN have for me to continue doing there?" Answer: After June 17, nothing.Miles O'Brien: Coming soon to "American Morning." Seeks cardboard box near good schools.Jack Cafferty: CNN "bright bulb" who now gets to sleep in.