Such a move would likely finish off a fragile power sharing pact which has been deadlocked for months while the parties fight over control of key cabinet posts.
Analysts had seen the pact as the best hope for averting total collapse in Zimbabwe, where hyper-inflation means prices double every day and a cholera epidemic has killed more than 1,100 people.
Mugabe said on Friday he had invited Morgan Tsvangirai, leader of the opposition Movement for Democratic Change (MDC), to be sworn-in as prime minister in a shared government under the September 15 pact.
But Tsvangirai’s MDC said it had not received an invitation, and the leader said on Friday talks on a unity government could collapse over abductions of MDC supporters which he blamed on Mugabe’s party.
ZANU-PF officials said it would end its annual conference with a resolution urging Mugabe to urgently form a government. Mugabe is due to address the conference later on Saturday.
"The conference will resolve that President Mugabe implement the November SADC resolution to immediately form a government, most probably in the next week," a senior ZANU-PF official told Reuters.
"We have waited for too long and our people are impatient and suffering. With or without the MDC, the government will have to be formed," the official, who declined to be named, said.
Zimbabwe has had no new government since elections in March, in which ZANU-PF lost control of its parliamentary majority for the first time since independence in 1980. Tsvangirai boycotted a June run-off vote to elect a president, citing violence against his supporters.
The regional Southern African Development Community (SADC) has been trying to end the impasse and last month ruled the parties should urgently form a government, splitting the key Home Affairs Ministry, which has been at the centre of the quarrel over cabinet posts.
The MDC, which accuses ZANU-PF of trying to relegate it to a junior role in any unity government, rejected that decision and has said it will only join a new government if its concerns are addressed.
Mugabe has told supporters to gear up for fresh elections if the political impasse continues. The MDC says it is ready for a vote but not on ZANU-PF’s terms.
Western countries and some African leaders have called for Mugabe, 84, to step down and the veteran leader on Friday told supporters his foes were trying to exploit the cholera epidemic to oust him.
Some analysts believe Mugabe is pressing ahead with forming a government because he knows the MDC will reject the move, and wants SADC to blame Tsvangirai for wrecking the power-sharing pact.