Burundi's president skipped regional talks Monday aimed at brokering a deal to end weeks of unrest in the country, choosing instead to campaign for his controversial third term.
Leaders of the five-nation East African Community (EAC) bloc had been due to meet Monday in Dar es Salaam.
"President Pierre Nkurunziza will not attend the summit," said spokesman Gervais Abahiro, adding that Foreign Minister Alain Aime-Nyamitwe would take his place.
Mr Nkurunziza will instead lead his presidential campaign in Burundi's central Mwaro and Gitega regions.
The crisis in Burundi surrounds Mr Nkurunziza's bid to stand for a third consecutive five-year term in office, a move branded by opponents as unconstitutional and a violation of a peace deal that brought an end to years of civil war in 2006.
More than 70 people have been killed in more than two months of protests and a failed coup attempt, with almost 144,000 refugees fleeing into neighbouring nations.
Parliamentary and local elections held last Monday were boycotted by the Opposition.
The UN electoral observer mission said the polls took place "in a tense political crisis, and a climate of widespread fear and intimidation".
Results are yet to be released.
Presidential polls are due on July 15 followed by senatorial elections on July 24.
During the first summit on May 13, a general staged a failed bid to unseat Mr Nkurunziza while the president himself attended the talks.
Mr Nkurunziza did not attend a second summit on May 31.
The EAC bloc includes Burundi, as well as Kenya, Rwanda, Tanzania and Uganda.
But Rwandan President Paul Kagame, who has called on Mr Nkurunziza to step down from power, is also not attending the summit, officials in Kigali said.
On Sunday, Burundian rebel general Leonard Ngendakumana, who took part in the failed coup in May, vowed further attacks until the government is overthrown.
COUP LEADER ON THE RUN
"After we saw that we could not succeed our coup on May 15, we found it was necessary to keep fighting so that we can push Nkurunziza to keep thinking about what he is doing and maybe just resign," Mr Ngendakumana told Kenya's KTN news channel in an interview.
"All those actions that are going on in the country, we are behind them and we are going to intensify them until Pierre Nkurunziza understands that we are there to make him understand by force that he has to give up his third term."
General Ngendakumana, a top intelligence officer, is an ally of coup leader General Godefroid Niyombare, who has been on the run since their attempt to seize power was thwarted.
"There was a need to organise that coup to make a change in the country because the situation was very bad," Ngendakumana said.
"Mr Nkurunziza and his team were leading the country in a situation of civil war, and we could not accept that our population our country were led into a civil war."
"They are trying to move towards an open civil war just to find a way to protect themselves," Ngendakumana said.