Fiji's army head, who is threatening a coup against the government, says the sooner the military acts the better.
Cmdr Bainimarama said that Mr Qarase had to step aside
In a TV interview, Cmdr Frank Bainimarama said the army would "find ways" to make Prime Minister Laisenia Qarase resign if he refused to do so.
He said he planned to appoint an interim civilian administration and hold elections at a later date.
But Cmdr Bainimarama did not specify a deadline, amid media reports he plans to act early on Monday.
Tension has been rising for weeks in the Pacific island nation amid a stand-off between Cmdr Bainimarama, the head of Fiji's military, and the prime minister.
A Friday deadline the military leader set for Mr Qarase to step aside has already passed.
Early on Thursday, the military staged night-time operations to secure strategic areas of the capital, Suva, in what it described as a training exercise.
'Sooner the better'
Speaking to Fiji One television, Cmdr Bainimarama said Mr Qarase had to step down.
"Our plan is for (Qarase) to accept the military demand for him to resign," he said.
If he resists, "we will find ways for him to resign", he said.
Asked when the military planned to act, Cmdr Bainimarama did not give a specific timing, saying: "What I can say is, the sooner the better."
Local daily the Sunday Post reported that troops planned to move early on Monday morning, citing unnamed sources.
Cmdr Bainimarama dismissed the report, calling it "rumours".
But in a Fijian-language TV interview, he said that "transition is expected to take place tomorrow as a deadline", Reuters news agency reported.
The feud between the two men goes back several months.
It relates to legislation that Mr Qarase is seeking to pass, which offers a pardon to people involved in the 2000 racially-motivated coup and allocates the ownership of coastal land to ethnic Fijians.
Cmdr Bainimarama played a key role in putting down the uprising and was at one point forced to flee for his life.
He has made it clear that he does not feel the government has done enough to bring its perpetrators to justice.