The return date for "Good Morning America" host Robin Roberts, who has been off the ABC morning show while she deals with medical issues, will be in May 2013 at the earliest, and more likely June, reports TMZ.com.

An earlier return could be risky because her immune system is still weak after undergoing a bone marrow transplant, the report notes. As previously reported, Roberts is undergoing treatment for MDS, a bone marrow disorder that affects the production of blood cells.

Her doctors say she’s making progress and is right on schedule, the report notes. But executives were hoping Roberts could return as early as February, which appears unlikely, the piece adds.

When it does happen, her return could push "GMA’s" ratings even higher, providing more of a challenge for "Today" on NBC, the piece adds. After coming in second to “Today” for years, “GMA” recently moved ahead of its rival in the morning ratings battle.

Robin Roberts