Zanu-PF has given Mugabe less than 24 hours to quit as head of state or face impeachment. It also expels his wife Grace and names ousted VP Mnangagwa as the new party chief.
"I expect that the impeachment proceedings will now commence", he said.
The party also reaches out to the main opposition, the Movement for Democratic Change (MDC), seeking their cooperation to pass the necessary parliamentary votes.
Tshinga Dube, who was in Mr Mugabe's cabinet until he was sacked last month, described the president's defiance at "the last kick of a dying horse".
The embattled leader surprised Zimbabweans on Sunday, declaring on TV that he planned to remain as President.
Meanwhile, the Zimbabwe National broadcaster, ZBC, has been told to be on standby by the army as there could be another announcement from either Mugabe or the military tonight.
But when Mugabe addressed the nation on Sunday, he vowed to preside over a Zanu-PF congress in December. "All that people marched for on Saturday was pointless as his (Mugabe's) speech had no clarity and direction of where we are heading as a people".
Mugabe's wife Grace, 52, secured prime position to succeed him, sidelining the vice president, Emmerson Mnangagwa, who was sacked.
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Tillis battled intestinal issues since early 2016 and never fully recovered. "There will never be another Mel Tillis! ". According to his website, his career launched in 1956 when Webb Pierce recorded a song written by Tillis.
It now appears that the military has been continuing efforts to ease Mr Mugabe from power without being seen as forcing out the nonogenarian leader.
Zimbabwe's state-run broadcaster says ruling party members are summoned to a meeting Monday afternoon as talk of impeaching longtime President Robert Mugabe continues.
Chiwenga, the general who announced last week on Monday that if Mugabe does not act against his wife the army will move in, escaped arrest when he returned from China about two weeks ago after Mnangagwa had fled the country.
The influential Zimbabwe National Liberation War Veterans Association (ZNLWVA) said Monday it would invite Zimbabweans back into the streets for more protests until President Robert Mugabe steps down.
This follows hot on the heels of the vote of no confidence in Mugabe passed by Zanu-PF's 10 provincial co-ordinating committees (PCC) on Friday.
Mugabe meets the army chiefs before making a defiant televised address in which he shows no sign of leaving, frustrating widespread hopes he would resign.
"Your time is up", veterans' association leader Chris Mutsvangwa said at a press conference.
The process can take long, and during that time, Mugabe will likely be around.
Today, Zimbabwe is on the threshold of a new beginning, but before we could get carried away in the prevailing euphoria that comes with Mugabe's cathartic fall, we must ask and agree among ourselves the sort of future we would want to see.