(CNN) Actor George Clooney has called for action against multinationals, western tycoons and brokers who have profited from South Sudan's violent instability, warning policy makers that "if you don't care" what happens in South Sudan its problems "will end up on your doorstep."

"Global warming is making the desert larger, violence is moving people off the land -- and they are moving by the millions," the outspoken activist told CNN's Nima Elbagir on Thursday.

"You care not just because it is the right thing to do, which it is, but because at one point or another, it is something that we will be dealing with."

On Thursday, a report released by the organization Clooney co-founded, The Sentry, called for the United States and the European Union to expand sanctions and step up anti-laundering efforts to hamper what it calls South Sudan's "kleptocratic network."

This is not the first time The Sentry has focused on the oil-rich country, which plunged into conflict in 2013 after it split from Sudan two years before, following decades of war.

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