Paul Rusesabagina, the man who inspired the film Hotel Rwanda, says unless the term of the UN tribunal on the genocide is extended it will be a failure.
Hotel Rwanda tells Mr Rusesabagina's story
He has written to the UN chief asking for some governing Rwandan Patriotic Front members to face justice.
The RPF took control of Rwanda in July 1994, putting an end to the genocide organised by extremist Hutu leaders.
The mandate of the UN-backed war crimes court which sits in Tanzania to try the genocide ringleaders ends in December.
Some 800,000 Tutsis and Hutu moderates were slaughtered during the country's 100-day genocide.
Since 1997 the International Criminal Tribunal for Rwanda has convicted 28 people and acquitted five.
Earlier this month, it requested for the first time the transfer of one of its cases - against Fulgence Kayishema, who is still at large - to Rwanda.
Correspondents say if the request is granted other cases are likely to be moved to Rwanda.
"If the Arusha tribunal ends its functions having only considered one side of the problem, most of us (Rwandese) would see it as a biased tribunal, and instead of resolving the Rwandan unity problem, it would have worsened it," Mr Rusesabagina told the BBC's Great Lakes service.
Guilty verdicts: 28
Cases in progress:11
Cases awaiting trial: 8
Accused at large: 18
The BBC's Nduwayezu Bathazar in Arusha says the tribunal still has 11 cases to finish and there are 18 people at large.
Crimes committed by the RPF in 1994 are still under investigation and there have been no public indictments, he says.
"If this tribunal doesn't deal with guilty RPF members, it means their cases will be transferred to Rwanda," said Mr Rusesabagina, who wrote to UN Secretary-General Ban Ki-moon about his concerns on 22 June 2007.
"But those who would be in charge of these cases may have been involved in criminal acts, in which case they wouldn't rule against themselves," he said.
In 1994, Mr Rusesabagina - a middle-class Hutu married to a Tutsi with whom he shared four children - sheltered some 1,200 refugees at a hotel in the capital, Kigali, where he was the manager.
The film Hotel Rwanda told the story of how he used his influence to bribe military officials to secure a safe escape for refugees.
"I'm just a normal person. But as I've always defended human rights," he said about his letter to Mr Ban.
"I'm trying to be the voice of millions of Rwandese who have no-one to speak out for them."