At 85, Mugabe is in the twilight of a political career spanning more than half a century and has led ZANU-PF since the mid 1970s when the party fought a guerrilla war against white minority rule.
But the veteran leader was forced to share power with Prime Minister Morgan Tsvangirai’s Movement for Democratic Change (MDC) party after losing its parliamentary majority for the first time in March last year.
The coalition has been rocked by differences over how to share power and the MDC is pressing for reform of the security forces it accuses of being used by ZANU-PF to stifle dissent.
"May I state this clearly and categorically, as ZANU-PF the defence of our sovereignty rests with us and with no other. Any manoeuvres to tamper with the forces will never be entertained by us," Mugabe said while closing a ZANU-PF congress.
Many senior officers in the security forces fought in Zimbabwe’s war of independence and remain loyal to Mugabe. They have vowed never to recognise Tsvangirai as leader.
ZANU-PF and the MDC are involved in a round of talks to clear outstanding issues of a political deal signed last year.
The MDC wants the central bank governor and attorney general replaced, and party treasurer Roy Bennett and some senior officials sworn-in as deputy agriculture minister and provincial governors, respectively.
ZANU-PF passed a resolution on Saturday rejecting the demands and said, instead, the MDC should call for the removal of Western sanctions and persuade radio stations broadcasting from abroad to stop.
While Mugabe has managed to remain at the helm of ZANU-PF, a raging battle is underway over who will eventually succeed him, threatening the future of a party that had enjoyed uninterrupted rule from independence in 1980 till last year.
ZANU-PF retained Joyce Mujuru, 54, as Mugabe’s deputy while party chairman John Nkomo, 75, filled in the vacant second vice president position. He will be sworn in as Zimbabwe’s deputy president on Monday.
Mugabe on Friday condemned internal fighting over leadership posts in the party, saying this was "eating up" ZANU-PF but on Saturday the veteran leader said the party had emerged from the congress much stronger.
"We go back much stronger, a better focused party raring to go, to take on the enemy who has sought our ruin through sanctions," Mugabe said.
He accused Western countries of plotting to reverse seizures of white commercial farms to resettle blacks but said they would not succeed.