Sudan's government says it has not yet accepted the deployment of a larger African Union peacekeeping force in the Darfur region.
The refugees are at risk of starvation and disease
Earlier reports quoted a government spokesman as saying it would accept a larger force, provided it was used to contain and demobilise rebel forces.
Only a small African peacekeeping force has been allowed in so far to protect officials monitoring a ceasefire there.
Some one million people have fled violence creating a major humanitarian crisis.
Peace talks in Abuja involving representatives from the government and rebels have been making slow progress and have been adjourned until Thursday.
Sudan has already agreed to 300 AU troops in Darfur with a limited mandate to protect the organisation's monitors.
Nigerian President Olusegun Obasanjo, who is also chairman of the AU, has proposed sending about 2,000 AU troops to contain the rebels in a deal that would see Khartoum disarming the pro-government Janjaweed militia.
The talks had earlier threatened to collapse after rebels rejected plans to restrict armed groups to certain areas. This requirement forms part of an agenda for talks with Sudan's government.
Also on Wednesday, the European Commission announced a further 20m euros ($24m) in aid for Darfur, saying the situation in the region had not improved, AFP reports.
"The humanitarian situation in Darfur is still extremely
worrying, and by all accounts could deteriorate further," said Poul
Nielson, EU Commissioner for Humanitarian Aid and Development.
More than one million people have fled attacks by pro-government Arab militia - known as Janjaweed - whom the UN accuses of killing at least 50,000 in an 18-month reign of terror.
Khartoum denies it used the Janjaweed to quell an uprising by Darfur rebel groups last year.
It has promised the UN it will disarm the Janjaweed.
Progress at the talks in Abuja had been very slow.
More than 1m displaced
Up to 50,000 killed
More at risk from disease and starvation
Arab militias accused of ethnic cleansing
Sudan blames rebels for starting conflict
President Obasanjo announced on Tuesday that an agenda had been agreed - a day after the formal opening.
A UN Security Council session on Tuesday heard how the people of Darfur are still "scared" and "dying" because the Janjaweed have not been neutralised.
The Council meets again next week to decide whether to impose sanctions on Khartoum.
Meanwhile, the Red Cross says it is launching a big new airlift of relief supplies to Darfur, in the largest operation of its kind since the start of the war in Iraq.
It says it will use one of the world's biggest cargo planes to carry trucks and other equipment.