Sudan has agreed to the deployment of some 3,500 extra African troops in its war-torn region of Darfur.
Rwanda already has some 150 troops in Darfur
The soldiers, along with some 800 police officers, will be tasked with monitoring a shaky ceasefire between rebels and the government.
However, Sudan is stopping the existing 300-strong peace team from doing its job, a journalist who spent time with them has told the BBC.
The troops will still not be allowed to use force against combatants.
The African Union have confirmed that Sudan has agreed to reinforcements but could not confirm numbers and said nothing had been signed.
UN officials say they hope the new troops coukld be on the ground by the end of the month.
Sudan insists that their main mission will be to protect camps for the estimated 1.5 million people who have fled their homes.
It has refused to accept a peacekeeping mission, saying the troops are monitors.
There are currently some 300 Nigerian and Rwandan troops in Darfur, under the flag of the African Union (AU).
A United Nations resolution backs an expanded AU force in Darfur but last week, African leaders said they needed hundreds of millions of dollars to fund the extra troops.
South African journalist Benjamin Joffe-Walt told the BBC's Network Africa that Sudan would often refuse to give fuel to the AU monitors while its attack helicopters were in the air.
"When the helicopters returned, the fuel started pumping," he said.
Many of the observers said this was common, he said.
Mr Joffe-Walt said that morale in the AU team was low as a result.
In addition to the weak mandate, another problem they faced was that representatives from both the rebels and the army had to approve each report and they often refuse to do this if either side is accused of breaking the ceasefire.
"Most commanders say it is incredibly difficult to issue a report," he said.
It has not been possible to get any reaction to these claims from the AU.
Up to 50,000 people have been killed in what the United States says is a genocide against Darfur's non-Arab groups.
Some 10,000 are dying each month in the refugee camps from disease and malnutrition, says the World Health Organisation.
More than one million people have been displaced in the conflict
The conflict began in February 2003 when two rebel groups took up arms, accusing the government of ignoring Darfur.
Human rights groups and the US say the government then armed Arab militias, who conducted a scorched earth policy against black Africans.
The government denies backing the Janjaweed militia and blames the crisis on the rebels.