Museveni, appointed mediator last week by the five-nation East African Community (EAC), is to push stalled talks between Nkurunziza’s ruling CNDD-FDD party and opposition groups.
The veteran Ugandan leader said in a statement as he left for Burundi he would “establish a dialogue among warring political factions.”
But with the presidential elections now scheduled for July 21, Museveni has been left with only a few days to succeed.
Nkurunziza’s bid to stand for a third consecutive five-year term, despite a constitutional two-term limit, has sparked months of civil unrest and an attempted coup in mid-May.
Opposition groups say another term would violate a peace deal that paved the way to end a dozen years of civil war in 2006. There are fears the current crisis could plunge the impoverished, landlocked country back into civil war.
Both sides have made clear that their positions will not change.
Museveni must convince the president to step down, said opposition leader Leonce Ngendakumana. “It is black and white,” he said.
Presidential communication advisor Willy Nyamitwe said he hoped Museveni would convince the opposition to take part in polls.
Opposition and rights groups argue that weeks of protests and a violent crackdown by security forces mean free and fair elections are impossible.
The country has also been left without most of its independent media outlets, after several radio stations were attacked and destroyed in fighting during the attempted coup.
Museveni, who has led Uganda since 1986 and is one of Africa’s longest-serving rulers, is himself seeking re-election in polls next year.