Foreign oil supplies are vulnerable to unnatural disruptions from in-state conflict, exporters' interests, and non-state actors targeting the supply and transportation of oil resources. The political and economic instability caused by war or other factors such as strike action can also prevent the proper functioning of the energy industry in a supplier country. For example, the nationalization of oil in Venezuela has triggered strikes and protests in which Venezuela's oil production rates have yet to recover. Exporters may have political or economic incentive to limit their foreign sales or cause disruptions in the supply chain. Since Venezuela's nationalization of oil, anti-American Hugo Chávez threatened to cut off supplies to the United States more than once. The 1973 oil embargo against the United States is a historical example in which oil supplies were cut off to the United States due to U.S. support of Israel during the Yom Kippur War. This has been done to apply pressure during economic negotiations—such as during the 2007 Russia–Belarus energy dispute. Terrorist attacks targeting oil facilities, pipelines, tankers, refineries, and oil fields are so common they are referred to as "industry risks". Infrastructure for producing the resource is extremely vulnerable to sabotage. One of the worst risks to oil transportation is the exposure of the five ocean chokepoints, like the Iranian-controlled Strait of Hormuz. Anthony Cordesman, a scholar at the Center for Strategic and International Studies in Washington, D.C., warns, "It may take only one asymmetric or conventional attack on a Ghawar Saudi oil field or tankers in the Strait of Hormuz to throw the market into a spiral."