The top U.N. envoy for Sudan (search) gave a sobering assessment of the shattered country, warning violence was on the rise in the Darfur region and criticizing nations that have not made good on their promises to supply peacekeepers and cash.

Jan Pronk said humanitarian programs have been underfunded by 50 percent for 2005. Though humanitarian and development programs have a budget of $1.9 billion this year, they have received only $950 million.

But the international community's chief fault was getting involved in Sudan too late, he said Wednesday.

"That is creating a situation which is getting out of hand, because the longer a situation like this is lasting, the more difficult it is to change it," Pronk said in an interview.

Tension in the capital Khartoum remains a concern, he said.

Nonetheless, Pronk said he was encouraged that a peace deal signed in January between the Sudanese government and southern rebels remains on track despite the July 30 death of Vice President and former rebel leader John Garang (search). Officials were concerned his death could lead to new instability in the south after a recent peace accord ended a 21-year civil war there.

While Pronk linked some of Sudan's trouble to Garang's death, he also faulted the international community and the Sudanese government.

Addressing some of the ongoing problems in the south, he said theLord's Resistance Army (search), a Ugandan rebel group, has disrupted U.N. work in that area with new attacks.

"I am as positive on north-south as I used to be, but I do not want to conceal that there are risks," Pronk said. "LRA is bigger than we thought and it's important to say so."

In a briefing to the U.N. Security Council earlier in the day, Pronk ticked off the long list of problems afflicting Sudan.

He said the western region of Darfur had seen a spike in violence in recent weeks.

The Sudanese military said Wednesday its soldiers had inflicted "heavy casualties" in driving off hundreds of Sudan Liberation Army (search) rebels who overran the Darfur town of Sheiriaa (search) on Monday.

"The armed forces repulsed the attack of the aggressor forces, inflicted heavy casualties on them, and forced them to retreat," Sudanese army spokesman Lt. Gen. Abass Abdul Rahaman Khalifa told the official SUNA news agency.

The United Nations launched a peacekeeping mission to help oversee the north-south peace deal but has left it to 6,000 African Union (search) troops to bring stability to Darfur. Pronk said violence in Darfur has declined where the troops are stationed though other areas remain insecure.

The Sudanese government denounced the SLA and urged the United Nations to "shoulder its responsibility to avert an escalation of the situation," SUNA said.

Darfur exploded in violence in February 2003 just as the civil war with Garang's rebels was winding down in the south. Rebels from ethnic African tribes took up arms, complaining of discrimination and oppression by Sudan's Arab-dominated government.

The government is accused of unleashing ethnic Arab tribal militia known as the Janjaweed (search) against civilians in a campaign of murder, rape and arson. At least 180,000 people have died in the Darfur conflict — many from hunger and disease. The fighting has driven some 2 million people from their homes.

Pronk said he is still hopeful for a peace deal between the government and Darfur rebels by the end of the year. He urged the Security Council to make clear that anything less is unacceptable.

Despite the worsening violence in Darfur, Pronk said the AU peacekeepers were helping keep Darfur peace talks in the Nigerian capital of Abuja from breaking off.

"So far, the AU has been able to avoid an impact on the talks," he said. "People stay at the table — a year ago they would have left."

But a spokesman for the 53-nation African Union, Jean Baptiste Natama, said the SLA attack on Sheiria this week threatened progress at the Darfur peace talks.