Tammineni will joining YSRCP in the presence of YS Vijayamma on Thursday afternoon.
It may be recalled here that when Sitaram announced his resignation to the party membership, he said that he was not satisfied with the TDP's stand on bifurcation and therefore, resigning from the party.
The party under Naidu's leadership was functioning against the wishes and ideology of party founder NT Rama Rao, he alleged.
In his 10-page letter to Chandrababu, he mentioned that the latter's leadership was functioning against the wishes and ideology of late NT Rama Rao. As the party failed to protect the self respect of Telugu speaking people, he decided to quit the party, Sitaram said in the letter.