CNN is lopping an hour off “American Morning” in mid-October to lighten the load on co-anchors Soledad O’Brien and Miles O’Brien.

“I just don’t want to burn the guys out. The O’Briens are only human,” CNN/U.S. President Jon Klein told TelevisionWeek Tuesday when asked why CNN was cutting its signature morning show from four hours to three. The anchors are not related.

Effective Monday, Sept. 4, Heidi Collins and weekend man Tony Harris will become the main anchors of the 10 a.m.-to-noon weekday block, which will be retitled “CNN Newsroom.” Kyra Phillips and Don Lemon will be the main anchors of the 1-to-4 p.m. edition of “CNN Newsroom.”

“It’s a combination of lightening their load and the confidence we have in our team,” Mr. Klein said, referring to the new Collins-Harris team.

The changes in personnel and lineups come a week after CNN announced that longtime anchor Daryn Kagan is leaving the all-news network at the end of the month. CNN said the morning edition will expand to 9 a.m. to noon later in the fall.

CNN executives have focused on “American Morning” and will continue to do so, Mr. Klein said.

“It has increased its share [of the cable news audience from 6 a.m. to 10 a.m.] over last year and for four straight months,” he said.

“American Morning” runs well behind “Fox & Friends” on Fox News Channel in the ratings but well ahead of MSNBC’s combo of “Imus in the Morning” and news coverage.

CNN hired T.J. Holmes, an anchor and reporter from NBC-owned KNTV in San Francisco to replace Mr. Harris on the weekends.