Reddy met YSRCP President YS Jaganmohan Reddy and announced his decision.
Recalling how Jaganmohan had undertaken a fast in support of united Andhra Pradesh while in jail, Reddy complimented the YSRCP leader for his sincerity in fighting for the cause.
Observers feel that more Congress leaders from Seemandhra regions would join YSRCP in the coming days in view of the ruling party's decision to grant statehood to Telangana.
The Congress Working Committee (CWC) had endorsed the separate Telangana demand on July 30 and, since then, Seemandhra has witnessed widespread protests against the decision.