George Clooney at the White House

As George Clooney left the West Wing, he seemed surprised to see the waiting microphones, cameras and dozens of reporters and photographers.Doug Mills/The New York Times As George Clooney left the West Wing, he seemed surprised to see the waiting microphones, cameras and dozens of reporters and photographers.

Rarely has the power of a celebrity to draw attention to an issue exerted such a pull as on Tuesday, when White House reporters called an end to the daily briefing by press secretary Robert Gibbs to catch the actor George Clooney as he left a meeting with President Obama about the crisis in Sudan.

Mr. Clooney reported to Mr. Obama on his recent week-long tour of the Texas-sized southern Sudan; preparations are lagging there for a referendum in January that is expected to result in residents favoring independence from the Khartoum government but which could end up reigniting civil war and atrocities. As Mr. Clooney left the West Wing, he seemed surprised to see the waiting microphones, cameras and dozens of reporters and photographers.

Clutching a green notebook at his side, Mr. Clooney, in a crisp navy suit, dark tie and white shirt, held forth with authority about the conditions and players in the Sudan, and about the need for the United States, the United Nations and other countries to keep pressure on President Omar Hassan al-Bashir not to sabotage the vote to keep control of the oil-rich south. Mr. Bashir has been indicted for crimes against humanity for his role in the genocide in Sudan’s western Darfur region.

Only a few times did Mr. Clooney defer to his companion, John Prendergast, a founder of the group Enough, which works in Sudan and other African countries with a history of genocide and atrocities. Mr. Prendergast joked that he carries the actor’s bags.

While human rights groups have criticized the administration for not pressuring Sudan enough, Mr. Clooney and Mr. Prendergast praised the president, who in September at the United Nations publicly admonished Sudanese officials to permit a fair vote. But Mr. Clooney urged continued, tough diplomacy by world leaders to prevent bloodshed, rather than waiting until too late as they did in places like Sudan’s Darfur and Rwanda.

He was mildly critical of the British government, noting signs that the new coalition government in London is softening its policies toward Sudan.

In a statement about the meeting, a White House spokesman, Tommy Vietor, said that Mr. Obama “underscored the intensity of the United States’ efforts to ensure that the referendum be held on time and to urge the parties to choose the path of peace over renewed violence.” Mr. Obama described a “diplomatic and development surge in the South” by the United States along with international efforts, but said the outcome depends on the leaders of the mostly Arab and Muslim north and the Christian and animist south to “refrain from inflammatory rhetoric and continue negotiating in good faith.”

Mr. Clooney’s meeting with Mr. Obama came between an appearance on NBC’s “Today” show and a meeting on Capitol Hill with Senator Richard G. Lugar of Indiana, the senior Republican on the Senate Foreign Relations Committee, to be followed by an address to the Council of Foreign Relations.

Reporters engaged Mr. Clooney with a number of questions, all about Sudan. Only when he and Mr. Prendergast had walked off and were out of range of hearing did one reporter, Mark Knoller of CBS News, pretend to shout the question he really wanted answered: “So, Mr. Clooney, is there going to be an ‘Ocean’s 14’?”