The US has begun an operation to seize an oil tanker linked to Venezuela after tracking it across the Atlantic, a source with knowledge of the operation told CNN on Wednesday.

Venezuela has the largest oil reserves of any country on Earth. But the type of oil it has is difficult, and dirty, to process. Experts say ramping up production would be expensive, and dangerous for ...

Here are key facts about international oil companies in Venezuela, a country with the world's largest oil reserves thrown into crisis by the capture of President Nicolas Maduro by U.S. forces.