Citadel CEO Ken Griffin said Tuesday that the global economy is headed toward a recession if the Strait of Hormuz stays shut for much longer.

“Let’s assume [the strait is] shut down for the next six to 12 months — the world’s going to end up in a recession,” Griffin said on stage at the Semafor World Economy conference in Washington, D.C. “There’s no way to avoid that.”

As a result, the world is going to see a massive shift toward alternative fuel sources, including wind, solar and nuclear, he added. To be sure, the hedge fund leader thinks the consequences of the war would have been worse if the U.S. delayed any strikes until Iran’s military capabilities had grown.

Stocks have managed to rebound back to where they were before the U.S. first attacked Iran in February, but the optimistic sentiment among investors is contingent on the duration of the war in the Middle East. Many expect risks of an escalation in tensions between the two countries are not at all priced into the market.

Global economies especially in Asia remain vulnerable to spikes in oil prices, which remain elevated at around $100 a barrel. That’s off their highs during the conflict, but remain far above where they were before the war, at just below $70 a barrel.