Zuma addressed ANC supporters who gathered in Kliptown in Soweto on Wednesday to celebrate his 75th birthday.
The South African Communist Party (SACP) and Congress of South African Trade Unions (Cosatu) have called on the president to step down, saying they have lost confidence in him.
Zuma says the party’s alliance partners must know he didn’t join the ANC with a position but he joined as a young man who rose up the ranks through hard work.
He says there is little time left for him to finish his term, saying in December the party will have a new leader and has also made it clear he will leave office as state president in 2019.
“Even if you said tomorrow I must step down I will step down with pure heart but I will be ANC till I die.”