The Keystone pipeline has been moving crude to facilities in Wood River and Patoka, Ill., since 2010 and to sites in Cushing, Okla., since February 2011, according to the company's website.
One oil analyst said the Keystone suspension should not have any impact on U.S. gasoline prices. But "it may put pipeline safety and the environmental hazards that come with transporting petroleum back on the map for a while, Tom Kloza, chief oil analyst at the Oil Price Information Service, said in an email.
The shutdown comes amid delays over TransCanada's plans to build another $7 billion section of pipeline called the Keystone XL that would transport heavy tar-sands crude oil from Canada to Texas' Gulf Coast refineries.
Pipeline opponents argue the project is unsafe because it would be carrying heavy, acidic crude oil that could more easily corrode a metal pipe, which would lead to a spill. They also say refining the oil would further contaminate the air in a region that has long struggled with pollution.TransCanada says its pipeline would be the safest ever built, and that the crude is no dirtier than oil currently arriving from Venezuela or parts of California. President Barack Obama rejected TransCanada's original application for a federal permit to build the pipeline in January by after congressional Republicans imposed a deadline for approval that didn't allow enough time to address questions about the route through Nebraska. Since then, TransCanada has split the project into two pieces. The company has started construction on the southern section of the pipeline between Oklahoma and the Gulf Coast.