The Inter-Burundi Dialogue on the deadly political violence that has rocked the nation for over a year, killing at least 500 people, has repeatedly run into snags and Wednesday's cancellation was the latest glitch.
"The government of Burundi refuses to sit with presumed putschists," tweeted Evelyne Butoyi, a senator on the government delegation.
The dialogue is being hosted by former Tanzanian president Benjamin Mkapa to end the trouble that erupted after President Pierre Nkurunziza announced in April last year that he was running for a third term.
He was re-elected last July, fuelling a wave of violence, a brutal government crackdown and a failed coup bid, according to the authorities.
More than 270,000 people have fled the country, raising fears of a wider crisis in Africa's volatile Great Lakes region after the 1994 genocide in neighbouring Rwanda took place in the wake of similar ethnic tensions.
In the first round of talks in May, the official Burundi delegation refused to hold talks with key members of the umbrella opposition group -- the National Council for the Restoration of Arusha Agreement and Rule of Law (CNARED) -- and a major civil society movement.
The regime describes CNARED as a "terrorist organisation".
This time round, negotiators invited some CNARED members but not the group as an entity in a bid to get the talks going finally.
But Willy Nyamitwe, a presidential spokesman and also a member of the government delegation, tweeted that those invited for the talks included the likes of CNARED chief Jean Minani.
"They are being prosecuted and cannot be invited to the talks," he said.