Tribal leaders are desperate for the deployment of a U.N. peacekeeping force along Chad's border with Sudan to protect refugees and stop increasing spillover from the violence in Darfur.

The U.N. Security Council is considering a mission, with up to 10,000 troops, largely because Sudan's government has resisted efforts to send U.N. peacekeepers to Darfur itself.

But Chad's president is worried about inflaming tensions with Sudan, while U.N. Secretary-General Ban Ki-moon has warned the Security Council that peacekeepers would face "serious risks" of rebel attacks.

The two countries have strained relations because Chad supports the Darfur rebellion against the Sudanese government, and Sudan strongly backs Chadian rebels settled in Darfur, Western observers say.

Tens of thousands of Darfur refugees live in scorching, wind-beaten camps on Chad's side of the border, competing with Chadian villagers over scarce water and firewood. Various rebel groups and militias roam the vast region.

"We are waiting impatiently for the international force to arrive and protect both the border and the refugees," said Timan Deby, the sultan or traditional ruler of Bahai, a desert outpost in Chad near the Sudanese border.

More than 200,000 people have died since ethnic African tribesmen in Darfur took up arms four years ago, complaining of discrimination by the Arab-dominated Sudanese government. The U.N. blames the Sudanese government's counterinsurgency for the bulk of the atrocities. Of the 2.5 million people who have fled their homes, 230,000 have ended up in refugee camps inside Chad.

Along the frontier, clashes between ethnic groups and cross-border raids are "carried out with impunity," the British aid group Oxfam said recently. Dozens of civilians have been killed in recent weeks, Oxfam said.

So far, none of the 12 refugee camps have been attacked, but several villages have been plundered.

The region's governor, Atom Dillo, said the U.N. force was necessary to stop Sudanese infiltration into Chad, which he said was part of Sudan's strategy to destabilize its neighbor and prevent aid workers from helping Darfur refugees.

Chad's President Idriss Deby has accepted the idea of a U.N. mission on his border in principle. But Western officials in Chad say he is worried the force might be used as a starting point for deployment into Darfur, which would anger Sudan.

"He doesn't want to be seen as facilitating a possible invasion of a neighboring state, even Sudan," said one Western official, speaking on condition of anonymity because of the situation's sensitivity.

Ban said Deby has proposed that the U.N. mission be a civilian one. He told the Security Council last week that any peacekeeping mission should help keep peace in refugee camps and deploy at key points to prevent cross-border attacks. But he warned it would carry "serious risks."

Last year, Chadian rebels based in Sudan launched several raids, briefly seizing the major eastern Chad town of Abeche and attacking the capital, N'djamena. Reports of smaller clashes come almost daily.

Col. Vincent Tesnieres, who commands a 1,000-strong French force already deployed in Chad, accused Sudan of providing the rebels with the ground-air missiles that recently helped them down Chadian aircraft.

"What is striking is that we now witness a level of violence completely unknown to Chad before," said Serge Male, the head of the United Nations High Commissioner for Refugees in Chad.

The UNHCR says it has a contingency plan for up to 50,000 more people to arrive from Darfur. The agency is trying to relocate the Darfur refugee camps further east from the border to ease the strain on Chad's meager natural resources.

The Chadian army is trying to protect the Darfur refugee camps but can't do much because it needs to focus on protecting the border, said Gen. Kalimi Sangui Abdalla, who commands Chadian military operations on the eastern frontier.

"This is why we will welcome United Nations forces," he said.