An EU force of up to 3,700 soldiers, around half of them French, is due to deploy soon to the border with Sudan's troubled Darfur region.

But some EU countries have refused to make up a shortfall in vital resources, and the launch of the mission in the former French colony -- originally mooted for early this month -- has been delayed.

"We appeal to EU foreign ministers to live up to their commitments to the people of Chad and commit the needed troops and adequate equipment immediately," said the head of Oxfam in Chad, Roland van Hauwermeiren.

EU foreign ministers are due to meet in Brussels on Monday to discuss the deployment.

The force looks likely to arrive in the middle of a volatile period in eastern Chad, where government troops have been engaging at least three rebel factions in the heaviest fighting in months following the collapse of an October 25 peace accord.

Both sides claim to have killed hundreds of enemy combatants in the fighting.

"We're very concerned by the severe deterioration in security across the east of the country in the past week," said Van Hauwermeiren. "We're already struggling to meet people's basic needs and this outbreak of fighting could mean even more pressure on limited resources.

"If we are forced to suspend our work in the camps and areas of displacement in eastern Chad where we provide clean water and sanitation, the people living there will suffer severe consequences."

French Defence Minister Herve Morin said Last week that EU peacekeepers should start deploying in eastern Chad late this month or early in January, although they lack key equipment.

Last month French General Henri Bentegeat, head of the EU's Military Committee, said the planned force lacked 10 helicopters, a third medical facility and other equipment.