Elliot Manyika, chairman of a committee on the state of the party, told the party's annual conference: "The committee reaffirms the leadership of President Robert Mugabe as the leader of the party.
"There should be no debate on succession because there is no vacancy. The committee agreed to have harmonised polls which should be held in 2010."
The party's youth wing and women's league also backed the extension of Mugabe's term of office.
Absalom Sikhosana, the youths' chairman, said: "Our first resolution is we are always preoccupied with elections, we feel if they are harmonised we will have time for other things especially us as youths who are always campaigning."
Oppah Muchinguri, the women's league chairwoman, said Mugabe's continued reign was the only way they would be safe.
She said: "Women are saying you remain in power, that's the only way we can be guaranteed because there are too many people who want your position. We are happy you said there are no vacancies."
Nathan Shamuyarira, a party spokesman, said: "There is a feeling in the party that it would be a good thing to merge the parliamentary and presidential elections in order to save money."
|"Zanu-PF has no candidate to succeed Mugabe and the party is unelectable, that is why they want to delay the presidential elections" |
Nelson Chamisa, spokesman for
the opposition Movement for Democratic Change
Mugabe would need the party's central committee and parliament to approve an amendment to the constitution to extend his mandate
However such a vote should be a mere formality given the party's majority in parliament.
Opposition politicians say Mugabe is trying buy time while his party decides on a candidate for the next presidential elections.
"Zanu-PF has no candidate to succeed Mugabe and the party is unelectable, that is why they want to delay the presidential elections," Nelson Chamisa, spokesman for the opposition Movement for Democratic Change, told AFP news agency.
Although Mugabe appeared to endorse Joyce Mujuru, the vice-president, as his successor when she was elected as the party's deputy leader two years ago, he has since criticised infighting among ambitious senior party members.
John Nkomo, the parliamentary speaker, indicated last month that he would be interested in succeeding Mugabe, telling journalists: "Why would I vie for the vice-president's position when there is the presidency?"
Analysts have said that an extension of Mugabe's presidency could worsen the economic situation. Unemployment is already above 80 per cent and inflation has run into four figures.
Mugabe is one of Africa's longest-serving rulers having been in power for 26 years, first as prime minister in the independence government and then as president after 1987.
In 2002, he narrowly won a presidential race against Morgan Tsvangirai, the leader of the Movement for Democratic Change. The opposition refused to accept that result, saying polling was swayed by vote-rigging, violent intimidation of voters and corruption.