KHARTOUM - Peacekeepers in Sudan's Darfur region are still struggling to get hold of vital helicopters more than 18 months after arriving because of competition from other conflict zones, a senior U.N. official said on Sunday.

The joint United Nations/African Union UNAMID force currently has no military helicopters, despite high-profile appeals for countries to provide them, said Susana Malcorra, head of field support for the UN.

The shortage was hitting the force's ability to react to security incidents in the remote western territory, which is about the size of Spain, she added.

Malcorra said UNAMID needed 24 military helicopters across Darfur but so far had only received promises of five from neighbouring Ethiopia, due to be delivered in October.

She said the international community had shown its commitment to the force by supplying troops and training, but it was struggling to provide aircraft amid a global shortage of military helicopters.

UNAMID, which took over from an AU force in January 2008, was supposed to have 26,000 soldiers and police.