Malnutrition is increasing again in Sudan's Darfur region, where increased violence and lack of funds are hampering aid efforts, the UN has said.
Malnutrition is creeping back up to levels seen in 2004
Clinics have seen a 20% increase in severely malnourished children since January, a spokesman for the UN children's agency, Unicef, said.
The surge in fighting has forced some 200,000 people to flee, bringing the total displaced to over two million.
Mediators are trying to get the warring sides to reach a peace deal by Sunday.
The African Union has set a 30 April deadline for the government and rebel groups to accept their draft peace agreement which addresses power-sharing, wealth-sharing and security.
"This is decision time. No more procrastination, no more antics, no more delaying tactics. The eyes of the world are on you," said Ahmed Salim Ahmed, the chief AU mediator.
Jockeying for power
Nearly two years of the AU-mediated talks in Abuja between the Sudanese government and the two main rebel groups have failed to end a conflict regarded as one of the world's worst humanitarian crises.
Unicef is now warning that the situation is once again worsening.
"We need to raise the alarm bell," said Ted Chaiban, head of Unicef's mission to Sudan.
"We're losing ground. We need to stop this deterioration."
In the last three months alone, there had been 200,000 people newly displaced in Darfur, Mr Chaiban said.
In any other country that would be front-page news, he said.
"Southern Darfur has seen both government-rebel fighting but also jockeying for power between the rebel movements," Mr Chaiban said.
About a third of displaced people are cut off from aid as humanitarian agencies cannot reach them because of the fighting.
Aid agencies last year managed to bring the malnutrition rate below the emergency threshold of 15% but south Darfur was seeing those figures again, Mr Chaiban said.
"Admissions to therapeutic feeding centre where severely malnourished children go are up by 20% since January. Admissions in the supplementary feeding centre where moderately malnourished children go are up by 50%," he said.
Unicef had received only $15m of the $89m promised by donors so it was having to cut back on some aid programmes.
"We don't have the resources to buy nutritional supplies. It's a double jeopardy to have lack of security, lack of access and now lack of funding," Mr Chaiban said.
Sudan's government has consistently said the scale of the problem in Darfur is being exaggerated for political reasons.
The authorities in Khartoum deny backing the Arab Janjaweed militias which are accused of mass rape, killing and looting.
The government has reacted angrily to Tuesday's decision by the UN Security Council to impose sanctions on four Sudanese nationals accused of war crimes in Sudan's Darfur region.
The four include two rebel leaders, a former Sudanese air force chief, and the leader of a pro-government militia, accused of widespread atrocities.
It was "unfortunate and ill-timed" and sent a "negative message" that could undermine the African Union's peace negotiations, the official Suna news agency quoted a foreign ministry spokesman as saying.
"The efforts currently being exerted in Abuja have neared their end and what is needed now is support and not the use of the stick," spokesman Jamal Ibrahim said.