The nuclear escalation of the nearly eight-month conflict in Ukraine can only be the beginning of a global battle, New York University business professor Nouriel Roubini said, who predicted the 2008 crisis.

According to him, the world could also witness a nuclear conflict in Iran and, what worries the U.S. the most, China's war over Taiwan. He argues that there is already a cold war between the U.S. and China that could escalate into a "hot war" as President Xi Jinping seeks to unite China and Taiwan.  "In some sense, World War III has already started,” Roubini said. “It started in Ukraine because this conflict has broader implications that go well beyond Russia and Ukraine. It’s the beginning of something else.”

Speaking to Yahoo Finance, Roubini emphasized the geopolitical threats and what he calls the new Cold War that has erupted between the United States and China, as well as between the West and the "revisionist" powers, including Russia, China, Iran, North Korea and Pakistan.

"They're essentially challenging the economic, social, and geopolitical order that the U.S., and Europe, and the West created after World War II,” Roubini said, explaining this crisis could ensnare the U.S.

According to Roubini, in addition to Ukraine, another hot spot could be Iran. "The negotiations between the U.S. and Iran on the new nuclear deal are not going anywhere, and Israel is saying if [Iran is] going to become nuclear — and they're one step away from it — we're going to attack them,” Roubini said. At the same time, the U.S. and China are on a collision course as the two countries continue to clash on fronts from trade to labor and technology movement.  "I believe the next 5-10 years is going to be the time where there’s going to be a confrontation between the U.S. and China on the issue of Taiwan and that could be a trigger of this cold war becoming a hot war,” he said. “That’s how we get to World War III.”