Even with nearly 7,000 African Union peacekeeping troops stationed in Darfur, and more on the way, the only hope the United States holds for an end to the violence, senior officials said, is sputtering peace talks that have produced no tangible results in 16 months and are dissolving into a bitter power struggle among competing rebel factions.

At the same time, more than 100 members of Congress, Republicans and Democrats alike, are accusing the administration of appeasing the Sudanese government, despite its complicity in the deaths of at least 200,000 people in Darfur.

A sudden spasm of violence in the last month - including the first killings of peacekeeping troops - has taken hundreds of additional lives and sent at least 10,000 more Sudanese fleeing to refugee camps, further swelling the unmanageable multitude of displaced people. Last week, Antonio Gutteres, the United Nations high commissioner for refugees, called it "a very serious degeneration of the situation."

In Darfur, desperate refugees are now kidnapping Sudanese aid workers and holding them hostage in their teeming camps to gain attention for their grievances.

International aid workers trying to feed more than two million refugees say the roads in Darfur are so crowded with bandits and killers that they have to deliver food by air. But the Sudanese government has suddenly cut off supplies of jet fuel.

Anti-government rebels in Darfur are carrying out attacks in vehicles painted as if they carry aid workers. Government forces are attacking and strafing civilians from aircraft again, after promising the United Nations this year that they would ground their air force in Darfur.

"You can never really secure this area until you create a peace accord," Robert B. Zoellick, the deputy secretary of state, acknowledged for the first time this week. He called all other steps merely "holding actions" intended to "minimize the violence." He planned to leave for Sudan on Sunday, his fourth trip this year, to make another effort to end the fighting.

In an interview on Friday, he elaborated, saying, "the most that can be expected of the African Union forces is a rough peace." But, he added, "the events of the past few weeks have demonstrated that it is not a stable equilibrium."

The conflict in Darfur began in February 2003, when rebel groups attacked government positions, accusing the leaders in Khartoum of ignoring their region. The government struck back with a fury, enlisting local militias to massacre civilians and destroy entire villages.

The world was slow to acknowledge the problem and then begin pressing the Sudanese government to call off the attacks. In September 2004, the Bush administration stated that the carnage constituted genocide. But the killing continues, even increasing in recent weeks, after a reduction in violence over the summer. In fact, American officials and aid workers say the government still pays some of the militiamen, known as janjaweed.

Observing this, 109 members of Congress assailed the government's strategy, saying it "appears conciliatory at a time when the violence in Darfur grows worse and the plight of its victims more terrible," as a letter to Secretary of State Condoleezza Rice, signed by all of them, put it on Oct. 28.

Specifically, the lawmakers accused the administration of "engaging in a policy of appeasement" toward the Sudanese government, first by granting a waiver to the sanctions in place against Sudan so its government, "whose objectives are genocidal," could hire a Washington lobbyist to promote its views.

The letter also complained that the State Department office that monitors slave trafficking worldwide upgraded Sudan's ranking this fall, saying it was cooperating more.

"Those little tidbits and morsels are very important to the Sudanese," said John Prendergast, who was director of African affairs in the National Security Council in the Clinton administration. Now, he is a senior adviser for the International Crisis Group, a nonprofit organization.

The State Department has not responded to the letter from the Congress members. But it did put out a statement on the hiring of the lobbyist, Robert Cabelly, saying he would "provide a perspective on United States concerns and policy that would be useful in advancing the peace process." The lawmakers said Sudan was paying Mr. Cabelly $530,000. Mr. Cabelly said he did not want to comment.

Department officials vigorously deny the "appeasement" accusation, saying the members of Congress who signed the letter are trying to score political points. In addition, "people feel a kind of frustration," Mr. Zoellick said. "They want to have a solution."

At the same time, however, the State Department seems intent on playing down the surge in violence, unlike almost every other government and nongovernment entities involved. "We find it utterly incomprehensible that the government of Sudan" after previously showing restraint, "has suddenly decided to abandon such responsible behavior and resorted to the violent, destructive and overwhelming use of force not only against the rebel forces, but also on innocent civilian villages," said Baba Gana Kingibe, the African Union's special representative in Sudan, in a statement last month.

Mr. Prendergast complained that the Sudanese government was defying American, United Nations and European demands to end the violence, "and yet there is no cost for Sudan, no penalty.

"They are out of control now," he added, "but they have a complete state of impunity. In fact, we are giving them things."

But when Jendayi Frazer, the American assistant secretary of state for African affairs, was asked about the deadly new developments in Darfur, she said: "That's just a snapshot of the moment. You can't take a snapshot and get a full picture." Pressed later, she acknowledged that government aircraft had been spotted in the vicinity of militia forces attacking civilians.

Peace talks between the government and the Darfur rebels broke up Oct. 20 because the fractured rebel armies could not agree on who was in charge and what their strategy should be. The meeting was the sixth negotiating session since July 2004, and by most accounts the two sides are hardly closer to reaching a settlement than when they began.