Russia produced 10.49 million barrels per day (bpd) in December, down 29,000 barrels a day from November. Saudi Arabia's output dropped to 10.46 million bpd from 10.72 million bpd, according to Monday's data from the Joint Organizations Data Initiative in Riyadh.

This was the first time Russia became top producer since March 2016. Riyadh's crude exports fell to eight million bpd from 8.26 million bpd in November, the biggest monthly slide since May 2003.

The United States is in third place, producing 8.8 million bpd in December. At the same time, America is neck-and-neck with China as the world's largest crude importer, buying 7.88 million bpd of crude last year.

The growth in US production mostly came from the Texas' Permian Basin and Eagle Ford regions, which have better quality oil. However, local refineries can't process it because they are geared to process poorer quality crude from Canada and Venezuela. The US producers export the higher quality oil and import what they need from abroad.