Fighting in Sudan's Darfur region has increased since a peace deal was signed two months ago, the head of the United Nations mission in Sudan has said.
Some 2m people have fled three years of fighting
Jan Pronk said people had been given distorted information about the deal, meaning it had not won popular support.
Only one of the rebel groups signed it and all deadlines for implementing the agreement have so far been missed.
The insecurity has meant the estimated 2m people displaced in the three-year conflict are unwilling to go home.
The BBC's Jonah Fisher in Khartoum says Darfur's peace agreement has brought only more conflict and confusion.
Two months ago, after tortuous negotiations, Western diplomats pushed through a deal between the Sudanese government and a faction of the Sudan Liberation Army rebels.
But since then Darfur has seen more violence with militias loyal to the government carrying out numerous small-scale attacks and rebel movements fighting amongst themselves.
Our correspondent says in Darfur's camps, public opinion has crystallised against the deal.
Faced by this depressing reality Mr Pronk - one of the deal's key architects - says more is needed to make the agreement workable.
"We should stick to the text as it is but add a lot to it," he told journalists in Khartoum.
This included international security guarantees and more money to give people confidence, he said.
But Mr Pronk defended the deal despite warning over the weekend that it could collapse without further concessions.
"The first priority is implementation, implementation, implementation... It's non-implementation of the text which is creating a problem, not the text," he said, Reuters news agency reports.
The UN is conducting the world's largest humanitarian operation in Darfur, where more than 200,000 people are thought to have died, most killed by pro-government militias.
Rebel forces took up arms in February 2003, accusing the government of discriminating against Darfur's black Africans in favour of Arabs.
Over the weekend, the African Union (AU) agreed to extend its stretched peace mission to Darfur until the end of 2006 at the request of the UN.
About 7,000 AU troops are in the vast region attempting to contain the violence.