Zambian President Edgar Lungu has sent former president Kenneth Kaunda to Harare to try to convince President Robert Mugabe to step down in a "dignified exit" after the military seized power last week.
The ruling party removed Mugabe as Zanu-PF president and first secretary on Sunday and lawmakers from the ruling party were due to meet at the party headquarters on Monday to discuss impeaching the 93-year-old leader.
"Dr Kaunda used the presidential jet and has already arrived in Harare," a senior government source told Reuters. Kaunda is also 93 years old.
Botswana President Ian Khama has also called on Zimbabwe President Robert Mugabe to end his attempts to remain in office.
The military intervention, which political sources say could pave the way to a national unity government after 37 years of Mugabe rule, also presented "an opportunity to put Zimbabwe on a path to peace and prosperity", Khama told Reuters.
"I don't think anyone should be President for that amount of time. We are Presidents, we are not monarchs. It's just common sense," Khama said.