U.S. Secretary of State Colin Powell visits Sudan Tuesday to urge Khartoum authorities to rein-in Arab militiamen accused of massive human rights abuses in the western Darfur region. Mr. Powell is to meet with Sudanese President Omar el-Bashir and also visit displaced people in Darfur.

Mr. Powell, who joined President Bush at the NATO summit in Istanbul, will break away from the Bush party to make the first visit to Sudan by a U.S. Secretary of State since 1978.

The U.S.-Sudanese relationship, all but frozen for a decade, has improved since last year amid anti-terrorism cooperation and gains in Sudan's north-south peace process.

However, progress has stalled because of the crisis in Darfur, where militiamen backed by the Sudanese government have driven more than a million people from their homes with scorched-earth tactics against local rebels.

At a news briefing State Department deputy spokesman Adam Ereli said that in talks with President el-Bashir and other Sudanese officials, Mr. Powell will make it clear that future U.S. relations with Sudan depend on action against the "Janjaweed" militiamen and opening the stricken region to outside help.

"Our message to the government of Sudan will be very clear and direct. Stop the Janjaweed violence," he said. "Remove all obstacles to humanitarian access. Cooperate fully with international monitoring, and agree to engage in political talks with the Darfur armed opposition. Normal relations with Sudan, the Secretary has also made clear on numerous occasions, are not possible unless and until there is a final north-south peace agreement and an end to the violence in Darfur."

Officials say Mr. Powell will have an evening meeting with Sudanese leaders in Khartoum and fly to the Darfur regional center of El Fasher Wednesday, where he will visit displaced persons camps and meet relief workers.

Mr. Powell's Sudan visit will coincide with a similar mission by U.N. Secretary-General Kofi Annan and they are expected to meet and make a joint appeal for more international aid for Darfur refugees.

The Bush administration has called the destruction of African villages by the militiamen "ethnic-cleansing," and U.S. officials are examining whether the activity can be defined as genocide.

President el-Bashir promised more than a week ago to disarm the Janjaweed and other armed groups, but U.S. officials say they have not yet observed any follow-through.

The Bush administration has threatened travel and financial sanctions against militia leaders and Sudanese officials who support them.

The Khartoum government denies helping the Janjaweed but officials here say the militiamen are armed by the central authorities and get tactical support from government military aircraft.

The Darfur fighting, which erupted early last year, has killed more than 10,000 people. U.S. aid officials say hundreds of thousands of the refugees, many of whom had fled into Chad, could face death from hunger and disease unless massive aid arrives soon.