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By Andrew Heavens

KHARTOUM, March 10 (Reuters) - A surge of bandit attacks has forced the U.N. to halve deliveries of emergency food in Sudan's war-torn Darfur region, aid officials said on Monday.

The U.N.'s World Food Programme (WFP) said an increase in attacks on its road delivery convoys in Darfur coincided with a cash crisis threatening to ground its air link to the region.

"This is an unprecedented situation," said the WFP's Sudan representative Kenro Oshidari.

"Our humanitarian air operation for aid workers could be forced to stop flying because we have no money, at a time when our helicopters and aircraft are needed more than ever because of high insecurity on the roads."

The WFP said 45 contract trucks had been hijacked since the start of the year, along with six of its own passenger vehicles.

Twenty-three drivers were still unaccounted for and 37 trucks were still missing, the agency added.

In the latest incident, a WFP vehicle was seized outside the gates of the agency's base in the North Darfur town of Kutum on Sunday morning. The driver escaped unharmed.

The WFP said it was delivering about half the amount of food aid it would expect at this time of year because of the hijackings and the reluctance of new drivers to come forward.

Demand for food aid was about to surge in the build up to the May-October rainy season.

"If WFP cannot maintain deliveries it will be forced to reduce rations in some areas," said WFP spokeswoman Emilia Casella.

AIR BRIDGE

Agencies are running the world's largest aid operation in the western Sudanese region of Darfur where international experts estimate five years of conflict have killed 200,000 people and driven 2.5 million from their homes.

Washington calls the violence genocide, a charge the Sudanese government rejects. It blames Western media for exaggerating the conflict. Numerous peace efforts have failed because of rebel divisions and continuing clashes.

The WFP said it would have to shut down its humanitarian air service by the end of the month unless more funding came in.

The agency's 24 aeroplanes and helicopters transport more than 8,000 aid workers around the region every month and carried out 267 emergency medical and security evacuations and relocations in 2007.

The WFP said it needed $6.2 million a month to run the air service but so far had no confirmed donations for this year's budget.

"It is the only way we can visit many of our programmes," said Alun McDonald, spokesman for the charity Oxfam's Sudan operation.

"With the insecurity, the hijackings and the attacks on our staff, most of the roads in Darfur are unusable at the moment."

Oxfam in September warned it could pull out of Darfur if the security situation worsened. (Editing by Keith Weir) (For full Reuters Africa coverage and to have your say on the top issues, visit: http://africa.reuters.com/ )

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