|Zimbabwe's Mugabe faces looming resignation deadline|
Proceedings could begin as soon as Tuesday when parliament meets.
Mr. Mugabe's grip on power has weakened since the army intervened on Wednesday, in a row over who should succeed him.
The crisis began two weeks ago when the 93-year-old leader sacked his deputy Emmerson Mnangagwa, angering army commanders who saw it as an attempt to position his wife Grace as next president.
Zimbabwe has since then seen huge street rallies, with demonstrators, including the country's influential war veterans, demanding his immediate resignation.
During the 20-minute address, the president, who was flanked by generals, made no mention of the pressure from his party and the public to quit.
Instead, he declared that the military had done nothing wrong by seizing power and placing him under house arrest.
"Whatever the pros and cons of how they [the army] went about their operation, I, as commander-in-chief, do acknowledge their concerns," he said, in reference to the army's move last week to take over the state broadcaster in the capital Harare.
He also said "the [Zanu-PF] party congress is due in a few weeks and I will preside over its processes".
Before Mr. Mugabe's speech, Mr. Mnangagwa was named as Zanu-PF's new leader and candidate for the 2018 general elections, while Mr. Mugabe's wife was expelled.
After Mr. Mugabe's speech, Zanu-PF chief whip Lovemore Matuke was quoted as saying that the resignation ultimatum was unchanged.
He added that impeachment proceedings could be launched on Tuesday in parliament. This would require a two-thirds majority in both chambers.
Mr. Mnangagwa, a former state security chief, is nicknamed "the crocodile" for his perceived shrewdness. He fled Zimbabwe after his sacking a fortnight ago, but has since reportedly returned.
The War Veterans Association, which used to back Mr. Mugabe, now says it is time for him to step down.
"Thirty-seven years, you have had your time, you are toast now politically," association head Chris Mutsvangwa told the BBC.
"Please give the country a chance, let it move to the next page."
Opposition leader Morgan Tsvangirai said he was "baffled" by the president's address.
"He's playing a game. He has let the whole nation down," he told Reuters news agency.
Mr. Mugabe has led the country since it gained independence from Britain in 1980.