China is to overtake the United States to become the world's biggest oil importer within a year and a half, Goldman Sachs said on January 9.

U.S. oil imports have slid by 40 percent over the past several years as technological innovation in areas such as shale gas has boosted output, while demand has soared in China, Jeff Currie, head of commodities research for the investment bank, told a strategy conference in London.

"Within the next 12 to 18 months, China's going to surpass the United States as the biggest importer of oil in the world," he said.