KHARTOUM: The UN and its aid partners in Sudan need almost $1 billion to help victims of the Darfur conflict and wars in South Kordofan and Blue Nile states, officials said Wednesday, as funding becomes harder to obtain for the country's long-running crises.

In one of the world's largest humanitarian operations, the agencies hope donors will provide $983 million this year to support food, water, sanitation and other assistance for 4.3 million needy people, most of them in the Darfur region which has endured a decade of insurgency and other conflicts.

But officials admitted they face competition from global "hot spots" such as Syria, while restrictions on access to Sudan's needy led to reduced donor backing in 2012.

"Hundreds of thousands of people have been affected by fighting in Sudan over the last year," said Mark Cutts, head of the UN's Office for the Coordination of Humanitarian Affairs.

"Hundreds of thousands of people remain homeless, continue to live out in the open or in very temporary accommodation, often in really appalling conditions," Cutts said.

He spoke to aid workers and diplomats at the launch of the UN's 2013 Work Plan developed with aid agencies and Sudanese authorities.

The funding target is down slightly from last year even though the UN aims to assist 100,000 more people.

"That is because the effect of the separation of South Sudan has been more fighting in parts of the country," Cutts said.

In South Kordofan and Blue Nile, the UN plans to assist 700,000 people affected by war which began two years ago between the government and rebels. Khartoum alleges the insurgents are backed by South Sudan, which separated in July 2011 under a peace deal that ended a 23-year civil war.

Farther west in Darfur, battles between Arab tribes this year displaced or severely affected at least 100,000 people. Aid workers said it was the region's largest uprooting of the population in years.

In 2013 the UN was already planning to reach 1.4 million people in camps for people displaced by Darfur's long conflict, which began when rebels from black tribes rose against the Arab-dominated Khartoum regime.

"Ten years after the emergency in Darfur began it is unfortunate that we still have nearly one and a half million people in camps," said Cutts, adding that a priority is to promote "self-reliance" and reduce aid dependence.

Last year the UN appealed for roughly $1 billion in assistance to Sudan but by mid-November had received only 53 percent of that, a sharp drop from 2011.

The Work Plan said "donor fatigue" with Sudan, and restrictions on movement of aid agencies, were among factors that reduced funding.

"Restricted humanitarian access, due to conflict-related security concerns and government regulations... has seriously affected the implementation of many sector activities," the 128-page Work Plan says.

It referred particularly to South Kordofan and Blue Nile, where not only foreign aid workers but also diplomats and reporters have been severely constrained in their movements.

UN humanitarian operations director John Ging in January spoke of "people having to rely on roots and leaves" to survive in South Kordofan and Blue Nile. But Sudan's top aid official, Suleiman Abdel Rahman, told the Work Plan meeting that there is "no humanitarian crisis" in those two states.

Recent discussions with the government led to directives that grant "a reasonable level of access" to the UN and international aid groups throughout Sudan including South Kordofan and Blue Nile, said Ali Al-Za'tari, the UN's top official in Sudan.

"They are not the ideal," but they are a positive step, he told reporters. If properly implemented, the new directives should show that things have changed, Za'tari said.

He added that funding suffered last year because donors focused on newer global problems.

"I hope that the trend is going to be reversed in 2013," he said.