Burundi's last rebel group has signed a ceasefire deal with the government at a ceremony in Tanzania.
Previous deals with the FNL have failed to end the war
The deal with the National Liberation Forces (FNL) is supposed to end 13 years of civil war between ethnic Tutsis and the Hutu majority.
Other Hutu rebel groups have already laid down their arms - including those loyal to Pierre Nkurunziza, who was elected president last year.
But a government crisis at home threatens to overshadow the event.
Earlier this week, Vice-President Alice Nzomukunda resigned, saying corruption and human rights abuses were hampering government business.
On Wednesday, South African mediators were still trying to overcome the FNL's reservations about the proposed ceasefire agreement, including the details of how its fighters are integrated into the Burundian army.
"The signing of the agreement will hopefully silence the guns," said South African special envoy Kingsley Mamabolo at the ceremony in Dar es Salaam.
The BBC's Prime Ndikumagenge in Burundi says, however, that before leaving for Tanzania, reporters were more keen to know President Nkurunziza's reaction to Mrs Nzomukunda's resignation than his expectations for peace.
Mrs Nzomukunda said it had been a hard decision to resign
The same was true for FNL leader Agathon Rwasa, who when contacted by local radio stations about the ceasefire deal was first asked to react to the vice-president's walk-out.
Her declarations that the ruling party chairman was corrupt and hampering the nation's progress have hit straight to the core of government, our correspondent says.
But Burundians in the west and north-west of the country where the conflict has been going for the last 13 years have been anxious for a successful outcome in Dar es Salaam, he says.
Earlier attempts at peace talks between the FNL and the government have failed.
Since independence in 1961, Burundi has been plagued by tension between the dominant Tutsi minority and the Hutu majority.
Posts in the previously Tutsi-dominated army have been split equally between Tutsis and Hutus as part of a peace deal with other Hutu rebel groups.
Hutu former rebel leader Pierre Nkurunziza was last year elected president after a transition period.
More than 300,000 people have died in the war sparked in 1993 by the assassination of Burundi's first Hutu head of state and democratically-elected president, Melchior Ndadaye.