Although U.S. imports of crude oil are down overall, the share of oil from the nation's top three suppliers soared to its highest levels in four decades in 2013, according to the U.S. Energy Information Administration.
Canada, Saudi Arabia and Mexico accounted for about 61% of total net U.S. oil imports last year, up from 55% the year before, the agency said. That's their biggest share since at least 1973.
"These three countries provided almost three out of every five barrels of oil imported into the U.S. market last year," the report said.
But that share increase is mostly due to the declining U.S. reliance on foreign oil and natural gas overall, the report said. Total net imports from Canada, Saudi Arabia and Mexico actually slipped by 1.5% last year on a barrel basis.
Net U.S. energy imports plunged last year to their lowest level in two decades, according to the agency. Advances in technologies such as hydraulic fracturing drove net imports down 19% in 2013, from 2012.
The U.S. is forecast to surpass Saudi Arabia and Russia as the world's top oil producer by 2015, and edge closer to energy independence in the next two decades, according to a report by the International Energy Agency.