With violence sharply increasing in Sudan's Darfur region, the Bush administration is engaged in a delicate balancing act of prodding the government in Khartoum to take steps to end the terrorism while encouraging it to believe relations with the United States are on the cusp of improvement.

Deputy Secretary of State Robert B. Zoellick next week will make his fourth trip to Sudan in seven months, a sign of the importance the Bush administration places on the issue. The administration's efforts to promote a resolution of the country's various ethnic conflicts suffered a setback when longtime rebel leader John Garang died in a helicopter crash in July, just weeks after he became first vice president of a national unity government.

The Bush administration played an instrumental role in the resolution of a two-decade civil war, which pitted the Islamic government in the north against rebels based in the mostly animist and Christian south. The administration has committed nearly $2 billion to implement the agreement as a lure for Khartoum to end the separate conflict in Darfur, located in western Sudan. Garang's replacement, Salva Kiir Mayardit, met in Washington this week with Vice President Cheney, Secretary of State Condoleezza Rice and Zoellick.

Meanwhile, Sudan is pressing for Washington to lift sanctions imposed years ago for Sudan's ties to terrorist groups. The Bush administration, which last year accused Sudan of permitting genocide in Darfur, is not yet prepared to take that step, officials say. But the State Department recently removed Sudan from the list of the worst offenders of human trafficking, and it has waived rules that prevented Sudan from hiring a Washington lobbyist. Earlier this year, the CIA flew Sudan's intelligence chief, who has been implicated in the Darfur attacks, to Washington for talks.

Those steps have alarmed some members of Congress, who accuse the administration of sending mixed signals and not being tough enough with Khartoum. "The administration is on the wrong track and sending exactly the wrong message," said Rep. Michael E. Capuano (D-Mass.), a co-chairman of the House Sudan Caucus.

At the same time, Congress has sent its own mixed signals. The House Appropriations Committee voted this week to kill $50 million sought by the administration to expand the African Union peacekeeping mission in Darfur.

The administration's deep involvement in Sudan is illustrated by the decision on human trafficking. Testifying before Congress this week, Assistant Secretary of State Jendayi Frazer said the administration decided to move Sudan from the lowest level -- known as tier 3 -- to "tier 2 watch list" because the Sudanese government presented Rice with a plan to end sexual violence against women when she visited Khartoum in July. But the plan, which calls for a public campaign against violence and the prosecution of rapists, was actually conceived by Zoellick, who presented it to the government two weeks before Rice's trip.

The conflict in Darfur broke out in early 2003 when two largely black African rebel groups attacked police stations and military outposts to protest what they called discrimination by Sudan's mostly Arab leaders. The United Nations and human rights groups have accused the government of arming and supporting militiamen, called the Janjaweed, to crush the rebellion. Estimates of deaths from the violence, disease or malnutrition in Darfur vary widely, ranging from 63,000 to 146,000, by the State Department, to more than 400,000 by private academic studies.

In July, Zoellick said "a fragile equilibrium" had been achieved in Darfur, largely because the militias were not attacking and the Sudanese military had pulled back.

But since then, peace talks have stalled, with rebels forces beginning to fight one another and new attacks launched by the Janjaweed with apparent government approval. Even AU forces and aid workers have come under attack, curtailing operations and leaving 650,000 refugees without humanitarian aid.

Baba Gana Kingibe, a senior AU official, bluntly criticized the government's involvement in the attacks at a news conference in Khartoum last month. He said "a number of coordinated offensive operations" had been launched by the Janjaweed and the Sudanese government. In one case, he said 400 militiamen on camels and horses rampaged through several villages, killing 32 people and burning 80 homes and shelters, while Sudanese helicopter gunships observed overhead.

Antonio Guterres, the U.N. commissioner for refugees, announced last month there was a "a very serious degeneration" in Darfur. "People are dying and dying in large numbers," he said.

Frazer, the assistant secretary of state for Africa, cautioned against dwelling too much on the current level of violence. In an interview, she said "this is a long process" that over time has begun to show progress. "If you look at a snapshot at one moment, you will miss that dynamic movement," she said.

The fighting among rebel forces, for example, is "one snapshot" but she said that was a "not uncommon effect of the end of a war" as groups jockeyed for position in negotiations. Zoellick, during meetings in Kenya, will attempt to bring the rebel forces together.