Two leaders jockeying for power in South Sudan, the world's youngest country, have enriched themselves, their associates, and their families while much of the public suffers on the verge of famine through a savage civil war, an investigative report released Monday alleges.

The report, which was pieced together over nearly two years by Washington-based policy and advocacy group The Sentry, calls upon the international community to impose sanctions to stop South Sudan President Salva Kiir and his rival and former vice president, Riek Machar, from profiting off the bloodshed.

Money that could have been used to improve living standards has, instead, been diverted to buy weapons for the ongoing conflict, which is motivated primarily by Mr. Kiir and Mr. Machar's competition to control natural resources, Sentry analysts concluded. The conflict, which has seen rape as a weapon of war and children recruited as soldiers, has displaced millions and resulted in tens of thousands of deaths.

"This is pretty explosive stuff," actor George Clooney said during a press conference Monday morning. Mr. Clooney co-founded The Sentry with rights activist and former US official John Prendergast.

A reporter asked Clooney whether Americans had been too optimistic when South Sudan gained independence in 2011.

"We always knew that there would be a difficult road ahead," Clooney responded, noting that war would have been inevitable had the people not been permitted to vote for their independence.

"Let's not forget out of what hell South Sudan was born," Mr. Prendergast chimed in. "It was a rocky birth, and everyone predicted it would be very, very difficult, and it has been, perhaps, even worse."

Today's problems of corruption and greed – and the international community’s complicity in them – date back to South Sudan's founding, Prendergast added.

"The fatal flaw in the international strategy has been that there was not a sufficient focus on the core rot at the foundation of this new government," Prendergast said. "The mass preponderance of resources were being stolen right out from under them."

Nearly half of the country's population relies on food assistance to get by, as The New York Times reports. But foreign benefactors have a hard time guaranteeing that their assistance reaches the people in need, Prendergast noted.

"In a kleptocracy, corruption isn't an aberration, it is the system. That is how governance has been hijacked and repurposed to enrich the top leaders," Prendergast said.

The report's recommendations include anti-money-laundering efforts, measures to protect innocent South Sudanese, and targeted US sanctions. Prendergast said he also supports a UN arms embargo, a proposal supported by a variety of organizations.

Louis Charbonneau, UN director at Human Rights Watch, told The Guardian last week it would be absurd to wait even a day longer to impose an arms embargo in South Sudan. At least four times, gunmen have attacked UN camps that house nearly 200,000 people, and UN peacekeepers have been criticized for abandoning their posts.

Amnesty International has been lobbying for the embargo since the conflict began in late 2013.

"While targeted sanctions are not a substitute for criminal accountability, in the short term they would serve as a deterrent to further violations, where none currently exists," said Elizabeth Deng, Amnesty International's South Sudan researcher.

"Even without an international arms embargo, states should unilaterally suspend arms transfers given the likelihood that arms would be used to commit human rights violations," Ms. Deng told The Associated Press.

The Washington Post Editorial Board argued last July that the United States needs to intervene.

"No other country played a bigger role in the creation of South Sudan than the United States," the board wrote, noting that the nation's independence was a signature project of then-Secretary of State Hillary Clinton under President Obama.

"Now is the time," the editorial continued, "for Mr. Obama to speak up for the people of South Sudan and let them know that the United States will not stand by as the infant state drowns in its own blood."