KHARTOUM, Sudan - The U.N. refugee agency appealed yesterday for additional money to help millions of people displaced by violence in Darfur as Sudanese, African Union and U.N. officials negotiate a peacekeeping deal for the region.

Despite a peace agreement signed in May between the Sudanese government and a single rebel group, fighting has only worsened in Darfur, a vast region of western Sudan where more than 200,000 people have been killed and 2.5 million forced from their homes since 2003.

"With constant fighting between government troops and rebels opposed to the [peace agreement], as well as regular attacks by Arab militia on African tribes, there is no prospect of return" for the millions of people living in camps, the U.N. High Commissioner for Refugees said in a statement appealing for funds.

Darfur is the world's largest continuing humanitarian effort, with about 15,000 aid workers, including 1,000 from abroad, according to the United Nations.

Twelve humanitarian workers have been killed in the last six months, and several aid groups have warned that the increasing violence is pushing them to the breaking point. A major French aid group announced earlier this week that it was pulling out of Darfur.

But the UNHCR, which has more than 100 staff working in most of Darfur's refugee camps, said it had no intention of leaving the region. Its appeal yesterday for $19.7 million would cover most of its costs for 2007 in Darfur, said Annette Rehrl, the agency's spokeswoman for Sudan.

"We are determined to stay in Darfur," Rehrl said by telephone. "We provide the basic protection, and if we go, everything goes."

The United Nations has accused Sudan's government of arming and directing militias of Arab nomads as part of its counterinsurgency tactics. The government has denied controlling the militias, and in turn has accused neighboring Chad of backing the rebel groups that refused a peace agreement.