Zimbabwe's ruling Zanu-PF party has endorsed President Robert Mugabe as its candidate for the 2008 election.
Mr Mugabe has made it clear he wants another term in office
Mr Mugabe, 83, has been in power since independence from Britain in 1980.
Correspondents say the move is a major setback for two party factions that wanted him to stand down in order to end the political and economic crisis.
The UN has warned that many people are facing starvation, and recent months have seen a harsh police campaign against opposition demonstrations.
The BBC's southern Africa correspondent Peter Biles says Mr Mugabe's critics within the party believe his leadership is deeply damaging and, with the economy now out of control, that he should step down.
The opposition group, Movement for Democratic Change (MDC), says it is appalled at the latest news - and there is likely to be deep disquiet across southern Africa, our correspondent says.
The US was quick to criticise Mr Mugabe's selection as a candidate.
"It's sad, it's outrageous and certainly we hope better for the Zimbabwean people," said state department spokesman Sean McCormack.
More than 80% of Zimbabweans are living in poverty, with chronic unemployment and inflation running at more than 1,700% - the highest in the world.
"The candidate for the party in 2008 will be the president himself. He was endorsed by the central committee," party spokesman Nathan Shamuyarira said after a meeting in Harare.
Parliamentary elections, scheduled for 2010, will be brought forward by two years to coincide with the presidential poll, he added.
Morgan Tsvangirai says he was badly beaten in police custody
Earlier, Mr Mugabe urged Zanu-PF members to stay united in the face of international and domestic opposition to his rule.
He branded the MDC as "violent", and said: "We can never entertain... a party that is walking the road of terrorism. We will not allow that in Zimbabwe."
However, MDC leader Morgan Tsvangirai says there has been a sharp escalation in violence against activists, with Mr Mugabe now using "hit squads" to crack down on group members.
Scores of activists were arrested and allegedly assaulted after police broke up a rally earlier this month. The police accuse the MDC of starting the violence.
On Thursday, an emergency southern African summit gave its public backing to Mr Mugabe despite international criticism over the crackdown on opposition activists.
The leaders, meeting in Tanzania, agreed that South African President Thabo Mbeki should try to promote political dialogue inside Zimbabwe.
They expressed solidarity with Mr Mugabe, urging Western countries to lift sanctions and also called on the UK to pay for land reform.
The UK and US governments are calling for sanctions beyond the current travel ban and assets freeze on senior officials.