Speaking to the AFP news agency by telephone from Paris, Nur said: "Spending the international community's money to host these factions will not bring peace to the people of Darfur.
"Recognising new factions will be endless, the rebels will split more and more, we will only see more movements."
'Future' at stake
Salim Ahmed Salim, African Union special envoy to Darfur, said: "What is at stake is the future of the people of Darfur.
"Genocide is a crime against humanity as a whole, not just against it's immediate targets. It therefore falls on the world at large to act."
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What is at stake is the suffering of the people of Darfur, those people who live in the IDP [Internally Displaced Camps], and the refugees and those people who live in constant fear for their lives."
The UN estimates about 200,000 people have died and two million forced to flee their homes in the last four years.
The armed opposition groups contend that Khartoum sent pro-Arab government forces to control the oil rich region. Non-Arab rebel groups took up arms against the government troops and have since splintered off into a multitude of rival factions.
Omar al-Bashir, Sudan's president, has rejected the claims, and called for unity in the Darfur region.
In his first tour of Darfur last month, al-Bashir said: "Tribalism and racism are illnesses. We should all promise each other that we abandon racism and division - we are all Sudanese and Muslims."
A peace deal with the government was signed at Abuja in Nigeria in May 2006, but it was only endorsed by one rebel group.
Nur charges that it was signed under intense pressure from the international community and eventually led to a deterioration of the situation in Darfur.
|Nur insists killing must stop in Darfur before|
negotiations can be held [AFP]
He said: "Going ahead with these talks now is repeating the mistakes of Abuja ... Peace is obtaining the trust of the people, what they will achieve in Arusha will be nothing more than a piece of paper."
UN and AU mediators in Arusha said the door remained open for Nur to join the talks.
Jan Eliasson, chief UN envoy, said: "We regret that Abdel Wahid Nur is not here. We hope that with this decision, he is not excluding himself from the final negotiations we are planning."
Mediators have said they are aiming to resume final settlement negotiations between the groups and Khartoum "within the next two months".
"It's the first time since Abuja that we've had so many leading rebel figures sitting together," Radhia Achouri, spokeswoman for the UN envoy to Sudan, said.
She said the factions would seek "to agree on confidence building measures such as finding means to contain banditry, ensure the best possible humanitarian access and give a voice to Darfur's civil society".