WASHINGTON - George Clooney used his Hollywood celebrity to draw attention Wednesday to the humanitarian crisis in the volatile border between Sudan and South Sudan, offering a firsthand account of the suffering as thousands forced to take refuge in caves because of daily aerial bombardments.

"What you see is a constant drip of fear," the actor and human rights activist told the packed room of the Senate Foreign Relations Committee as his every move was accompanied by the incessant sound of camera shutters clicking.

Just back from an eight-day trip to the region, Clooney described a secret, six-hour trip across the border to the Nuba Mountains, rocket attacks, death and destruction. He recalled how a 9-year-old boy had his hands blown off.

Teamed with John Prendergast, co-founder of the advocacy group the Enough Project, Clooney made a film that captured the images of crimes against humanity.

The four-minute video on two large screens showed refugees in caves, that 9-year-old boy with bloody arms and a woman marked by her wounds. Clooney was the guide throughout, and in the final image, he stood above what appeared to be a dead man splayed on the ground.

"How many more bodies until the Nuba Mountains become the next Darfur?" asked the video, which was released online.

More than two decades of fighting in the region gave way last year to an agreement to create the world's newest country, South Sudan. It seceded from Sudan last July amid hopes that have deteriorated into border clashes, deadly fighting and a standoff on oil.

Clooney said civilians who have farmed the fields are unable to work for fear of bombs dropping from military planes. Sudan has refused to allow aid agencies into the region. Nancy Lindborg, an official with the U.S. Agency for International Development, told the committee that 250,000 people are on the brink of a famine with the upcoming rainy season.

"These are not the cave people of the Nuba Mountains," Clooney said in an interview with a few reporters before his testimony. "People farm this land. They're hiding in these caves because they're attacked on a daily basis. The Geneva Convention calls that war crimes."

Sudan President Omar al-Bashir is wanted for war crimes by the International Criminal Court for killings and rapes committed in Darfur. Clooney referred to Bashir and others as war criminals.

Darfur has been in turmoil since 2003, when ethnic African rebels accusing the Arab-dominated Sudanese government of discrimination took up arms against it. The Khartoum government is accused of retaliating by unleashing Arab militias on civilians - a charge the government denies. The U.N. estimates 300,000 people have died and 2.7 million have been displaced.

The committee chairman, Sen. John Kerry, D-Mass., acknowledged that Americans' attention is often diverted by other crises around the world, but resolving the issues in the Sudan region is critical.

"Make no mistake: It is the leaders in Khartoum and Juba (South Sudan's capital) who must choose between a future of conflict and poverty or a future of security and prosperity. But we must not abdicate the important role the United States can play in helping to nurture that process just as we helped midwife the birth of this new nation," Kerry said.

Clooney, who called himself the "son of a newsman," said he understood the competition from other major stories such as the Arab Spring and jobs, but argued that the Sudan conflict should matter to Americans because of its affect on the price of gas at the pump.

Oil-rich South Sudan and Sudan, the keeper of the pipelines, have been at odds over oil and profits. Exports have stopped, putting pressure on oil prices worldwide. China receives about 6 percent of its oil from Sudan, and with that source shut off, must go elsewhere to buy oil.

"So we actually have a financial interest in this working out," Clooney told reporters.

Widely praised by Republicans and Democrats on the committee for his activist work, Clooney suggested that the Senate back tougher penalties similar to legislation sponsored by Reps. Frank Wolf, R-Va., and Jim McGovern, D-Mass., in the House, send a special envoy to China to seek their help with the Sudan dispute and freeze the financial assets of the Sudanese leaders to prevent them from buying weapons.

In his high-profile activist role, Clooney met with Susan Rice, the U.S. ambassador to the United Nations, on Tuesday, testified before the Senate panel on Wednesday and planned to meet with President Barack Obama at the White House and Secretary of State Hillary Rodham Clinton on Thursday.

"I'm not a policymaker," he told reporters. "My job is to just raise the volume."