Elections in Burundi, scheduled under a peace accord to take place by 1 November after years of civil war, will now take place in April.
President Ndayizeye discussed a new election timetable
President Domitien Ndayizeye made the announcement after a meeting with mediating regional leaders in Kenya.
The timetable for a new constitution has slipped due to disputes over power sharing between the Hutu majority and Tutsi minority.
A referendum to agree the constitution was to be held before an election.
It will now be held in November, the transitional president said on his return to the capital, Bujumbura.
He had been discussing the new election timetable with heads of state from Kenya, Uganda, Rwanda, Somalia and South African Deputy President Jacob Zuma.
The leaders said they took their decision to postpone the polls on advice from Burundi's electoral commission.
"Based on the reality on the ground, the summit accepts that elections cannot take place before 1 November 2004," the leaders' communique said.
Hutu rebels are to be integrated into the Tutsi-dominated military
Presidential elections will now be held in April, while local and legislative elections will be held a few weeks before, in March.
Correspondents say the delay is likely to further raise tensions between the two groups.
Under a power-sharing deal signed in August, the Tutsi minority will have 40% of government and national assembly posts, compared to 60% for Hutus.
This deal is intended to form the basis for the new constitution.
But the Tutsis want the presidency and vice presidency to alternate between the two communities.
Burundi's ambassador to Kenya, Stanislas Nsabuwanka, says another reason for the delay is the failure to find accommodation for many thousands of former Hutu rebels into the Tutsi-dominated army.
Some 300,000 people have been killed since the civil war broke out in 1993.
About 5,000 United Nations peacekeepers are in the country to support the South African-brokered peace process.