FRAZIER MOORE, AP Television Writer

NEW YORK - Robin Roberts said goodbye Thursday to her "Good Morning America" co-workers and audience. But only for a while.

"See you later. See you soon. I'll get back as soon as I can," she promised at the close of her emotional send-off from the show.

The "GMA" anchor was making her final appearance before starting medical leave for a bone marrow transplant. Her departure had originally been set for Friday, but in a last-minute change of plans she chose to exit a day early to visit her ailing mother in Mississippi, she told viewers.

During her absence, a number of famous faces will be subbing for her, including previously announced fellow ABC News colleagues Katie Couric, Barbara Walters, Diane Sawyer and Elizabeth Vargas.

In addition, Roberts announced that Oprah Winfrey, Chris Rock and Rob Lowe will be among the stand-ins, as well as the cast of the ABC comedy "Modern Family."

In June, Roberts had first disclosed that she has MDS, a blood and bone marrow disease. She will be hospitalized next week to prepare for the transplant. The donor will be her older sister, Sally-Ann Roberts, who was on hand for Thursday's broadcast.

But two of Roberts' on-air colleagues couldn't be there, thanks to the demands of breaking news.

From New Orleans, weather anchor Sam Champion voiced warm wishes, as did co-anchor George Stephanopoulos from the Republican National Convention in Tampa, Fla. He had left behind a gift for Roberts: a tap bell.

"Whatever you need, whenever you need it, ring that bell," he said.

With her and news anchor Josh Elliott in the studio, lifestyle anchor Lara Spencer presented Roberts with monogrammed matching pajamas for her and her sister.

"We're not crying tears of sadness," she told Roberts. "We're crying because we wish we could take this on for you."

One of Roberts' doctors, Dr. Gail Roboz, discussed the medical procedures that lie ahead.

"We're hoping the first 30 (days) is when we're going to see a lot of the recovery happening," said Roboz.

But Roberts replied, "I'm not even going to ask you when I can come back, because you have said, don't put a timetable on it."

Roberts, who has put a brave and usually smiling face on the challenges that await her, shared with viewers an inspirational quote: "Life provides losses and heartbreak for all of us. But the greatest tragedy is to have the experience, and miss the meaning."

Said Roberts, "I am determined not to miss that meaning."

As the program neared its end, the entire "GMA" crew gathered around the anchors' couch, displaying bracelets of support and bearing signs that promoted the "teamrobin" Twitter account.

Then Roberts' friend, country star Martina McBride, performed her Grammy-nominated song "I'm Gonna Love You Through It," an inspirational song about battling breast cancer. Looking on, Roberts mouthed the lyrics as her eyes welled with tears.

During the morning, the word "journey" had been mentioned repeatedly and "goodbye" was said in many ways.

"I take you with me in my heart," said Roberts at one point, addressing the full "GMA" staff. But wanting there to be no mistake, she added: "I WILL be back, just so you know."