South Africa's African National Congress (ANC) president Jacob Zuma hinted on Monday that his deputy Kgalema Motlanthe would become acting president, but stopped short of confirming this.
"I am convinced -- if given that responsibility -- he would be equal to the task," Zuma told reporters in Johannesburg.
Zuma said the African National Congress' candidates would be announced in Parliament "at an appropriate moment".
The ANC, together with Parliament, would ensure the election of a new president took place as speedily as possible, Zuma said.
He said the ANC expected a "smooth transition" as this was not a change of parties, but only of leadership in government. He called on all ANC ministers and deputy ministers to continue with their work, supported by the public service "which is not affected at all by the change."
Mbeki tendered his resignation on Sunday night after the ruling party informed him it would recall him from the post.
Motlanthe was ANC secretary general from 1997 to 2007, when he was elected ANC deputy president. He was previously active in the National Union of Mineworkers, where he became secretary general in 1992. Before that, he was education officer for the union.
He was detained in apartheid South Africa for about 11 months in 1967, and was sentenced to ten years imprisonment in 1977. Motlanthe was born in 1949.