By Hereward Holland
JUBA, Jan 30 (Reuters) - Conflict and food shortages could push up to half a million Sudanese refugees to flee to South Sudan in the next couple months if Khartoum does not allow aid agencies more access to its restive border regions, the World Food Programme said.
South Sudan seceded in July under a 2005 peace deal that ended a decades-long civil war with the north, but fighting has continued on both sides of the poorly drawn border.
The United States has pressed Khartoum to allow more aid in the South Kordofan and Blue Nile states, citing expert reports that said more than a quarter of a million people could be on the brink of famine there by March.
Sudan's ambassador to the United Nations this month dismissed concerns of a looming crisis in the two states, saying the situation there was "normal".
World Food Programme deputy executive director Ramiro Lopes Da Silva said more than 1,000 people per day have crossed into South Sudan over the last week, as many people as were crossing into Kenya from Somalia at the peak of the famine in the Horn of Africa last year.
"In a couple of months it is what is typically the hunger season both in Sudan and South Sudan and obviously the potential impact on those populations is very serious," Da Silva told reporters.
"There is a sense of urgency that the window for an effective intervention with the populations where they are is narrowing."
Fighting broke out in June between government forces and South Kordofan rebels who sided with the southern army during the civil war. The conflict spread to Blue Nile in September.
In South Sudan, aid agencies are already helping 83,000 Sudanese who have fled aerial bombardment and ground attacks in the two states.
The Sudanese government accuses South Sudan of continuing to support the rebel Sudan People's Liberation Army North (SPLM-N) in South Kordofan and Blue Nile, charges Juba denies.
WFP says they are already planning to feed 2.7 million South Sudanese this year, and are seeking donations to plug a cereal deficit which, according to preliminary estimates, could amount up to 500,000 tonnes.
Da Silva said WFP is lobbying Khartoum to allow more humanitarian access to Blue Nile and South Kordofan, but the government is worried the assistance may fall into the hands of combatants. (Additional writing by Alexander Dziadosz)