British Foreign Secretary Jack Straw is expected to arrive in the Sudanese capital, Khartoum, Monday evening to begin a visit aimed at stepping up pressure on the Sudanese government to end the devastating humanitarian crisis in the western region of Darfur.

Foreign Secretary Straw says he will first hold talks with the Sudanese president, vice president, and foreign minister about ways to end the humanitarian crisis in Darfur and international demands for the government to disarm marauding pro-government Arab militias known as the Janjaweed.

Before leaving for Khartoum Monday, Mr. Straw told reporters in London that he would press the government to show that it is serious about bringing to justice Janjaweed militiamen, accused of killing and raping tens of thousands of black civilians in Darfur and destroying their villages during the year and a half-long conflict.

"Everybody from [UN Secretary-General] Kofi Annan downwards is extremely concerned about this situation," Mr. Straw says. "We have sought to understand the government of Sudan's problems. Not all the problems are of their making; some of the problems are caused by the rebels, some of them are beyond anybody's control in this distant and sparsely populated area. But the prime obligation is on the government of Sudan and we look to them to meet their obligations."

The United Nations says nearly one and half million people have been displaced inside Darfur and another 200,000 are in neighboring Chad, creating the world's biggest humanitarian disaster.

The United Nations Security Council has given Khartoum until the end of the month to rein in the Janjaweed and restore order in Darfur or face international sanctions.

On Tuesday, Mr. Straw is expected to visit a camp in northern Darfur, which is home to some 57,000 refugees. There, he also plans to meet with African Union observers, who have been in the region to monitor a much-ignored cease-fire signed in April between the government and Darfur's two main rebel groups.

London says it is eager for the 53-member African Union to take the lead in solving the Darfur crisis, but has not ruled out military intervention of its own.

Khartoum has so far accepted 150 troops from Rwanda and the deployment of another 150 troops from Nigeria to act as a protection force for the 80 AU cease-fire monitors. But it has steadfastly rejected the idea of deploying an African Union peacekeeping force in Darfur, saying the government is capable of securing the region by itself.

The British foreign secretary's visit to Sudan comes as the government and Darfur rebel factions are starting a new round of peace negotiations in Abuja, Nigeria. The last round of talks, mediated by the African Union in Addis Ababa, Ethiopia, broke down after Khartoum refused to accept six demands the rebels set as conditions for the talks.

This time, Mr. Straw says he will be working closely with Nigerian President Olusegun Obasanjo, who is chairing the Abuja talks on behalf of the African Union, to help pressure the warring parties into reaching a political settlement.