Moved and angered by their visits to camps for Sudanese refugees, House members called on world leaders Thursday to pressure Sudan to stop the violence in the Darfur (search) region that has killed more than 70,000 people.

Actor Don Cheadle (search), nominated for an Oscar for his role in "Hotel Rwanda," joined lawmakers at a Capitol Hill news conference, drawing parallels to the violence that killed more than 500,000 people in Rwanda in 1994.

"People saw the film and said, 'Wow that's terrible. What happened? Wish I had known.' Now you know," said Cheadle, who accompanied lawmakers on the Sudan (search) trip.

The United Nations describes the Darfur conflict as the world's worst humanitarian crisis and the Bush administration has called it genocide. It began two years ago when rebel groups took up arms against what they saw as the Arab-dominated government's discrimination against Sudanese of African origin.

The government's counterinsurgency campaign and the violence of an Arab militia led to wide-scale abuse of the African population. An estimated 1.8 million people have been displaced. Many are now in refugee camps in Chad visited by lawmakers last weekend.

The delegation leader, Rep. Ed Royce, R-Calif., called on the U.N. Security Council to impose sanctions.

"This is not a problem for Africans alone to solve. The whole world must be engaged," said Royce, chairman of the International Relations subcommittee on Africa.

He said the main obstacles have been Russia and China, which have business interests in Sudan. Both nations have veto power on the U.N. Security Council.

Royce also called for expanding the size and mission of the African Union peacekeeping force, now monitoring an agreement aimed at ending a separate conflict in southern Sudan.

Lawmakers spoke of seeing refugees with missing limbs, shattered ear drums, or suffering from mental illnesses.

"I've seen a lot of things in my life but nothing prepares you for what we saw in this rather rapid trip through Chad and Sudan," said Rep. Jim McDermott, D-Wash.

Rep. Diane Watson, D-Calif., spoke of "250,000 souls sitting there" on the Chad-Sudan border "with blank stares in their eyes, still traumatized." She described pictures drawn by children of machetes cutting off arms and planes dropping bombs on villages.

The Sudanese government has usually denied using its air force against civilians, but Watson said "the children have not learned not to tell the truth."

An international aid organization said Thursday that the Sudanese air force had bombarded an area in South Darfur on Wednesday, chasing more than 200 people to a refugee camp. Field workers of the organization said they saw bombs exploding on the ground and an air force bomber circling overhead.

Sudanese government spokesmen could either not be reached or were unwilling to comment on the bombardment Thursday.

In Washington, Watson and Rep. Barbara Lee, D-Calif., said they discussed Darfur with President Bush and Secretary of State Condoleezza Rice (search) when a black congressional delegation met with them Wednesday.

Lee said she was "very optimistic that they're going to move forward more aggressively." Watson said she asked Rice if she would lead a delegation to Sudan, and Rice indicated she would.