On Monday Kate Gilmore, AI's executive deputy secretary-general, said: "Eyewitnesses in el-Fasher in North Darfur are telling us that Sudanese government military flights are flying in troops and arms on a daily basis.
"Displaced people in Darfur are absolutely terrified that the same soldiers that expelled them from their homes and villages may now be sent supposedly to protect them."
The UN Security Council will discuss on Monday a draft resolution proposing deployment of around 20,000 UN troops and police, despite Khartoum's rejection of any Darfur mission.
Omar al-Beshir, the Sudanese president, who opposes a deployment of international forces, has informed Kofi Annan that Khartoum would deploy 10,500 Sudanese troops to Darfur to provide security in the region.
Gilmore said: "The Sudanese government's 'protection plan' is a sham and must be firmly rejected.
"How can Sudan - which appears to be about to launch its own offensive in Darfur - realistically propose being a peacekeeper in a conflict to which it is a majority party and perpetrator of grave human-rights violations?"
The US government has also argued that Sudanese forces are not neutral and called for Khartoum to agree to a UN force to stop the violence that has continued in Darfur despite the signing of the peace accord in May.
The African Union has deployed a 7,000-strong peacekeeping force but due to inadequate funding it has decided to hand the operation over to an international force.
After mostly non-Arab rebels took up arms in early 2003, Khartoum armed Arab fighters to quell the revolt. Those fighters are accused of a campaign of rape and murder that Washington has called genocide.
Khartoum rejects the charge but the International Criminal Court (ICC) is investigating alleged war crimes in the region.
Some critics of the government have said that Khartoum has rejected UN troops because it fears those soldiers would arrest any officials likely to be indicted by the ICC, even though the two institutions are separate.
Some 300,000 people have died and more than 2.4 million have fled their homes since early 2003.