OPEC crude cargoes leaving for the United States in December dropped to the lowest level in at least five years, data from Refinitiv Eikon and market intelligence firm Kpler show.

Oil cargoes departing from OPEC nations to the U.S. fell to 1.63 million barrels per day (MMbbl/d) last month, down from 1.80 MMbbl/d in November and 1.78 MMbbl/d in October, the data show.

Saudi Arabia, the biggest producer in OPEC, and several others curbed supplies in the face of rising U.S. production and inventories, analysts said.

"Some of it was a decline in OPEC production," said Andy Lipow, president of Lipow Oil Associates in Houston. "But they're facing competition from U.S. shale and Canadian production."

OPEC and allies including Russia agreed last month to cut crude production beginning this month by 1.2 MMbbl/d, following a strategy to support prices when supplies overwhelm demand.

OPEC pumped 32.68 MMbbl/d last month, according to a Reuters survey, down 460,000 bbl/d from November, suggesting some members moved to reduce supplies ahead of the recent accord.

"Historically, Saudi Arabia has utilized crude export flows to the United States as a method of signaling the Kingdom's intentions, given the transparency of the U.S. market," said Reid I'Anson, an energy economist at Kpler.

Vessels last month carried about 534,000 bbl/d from Saudi Arabia to the United States, down from 632,000 bbl/d in November. Algeria sent 10,000 bbl/d, down 94,000 bbl/d, and Nigeria shipped 103,000 bbl/d, down by 48,000 bbl/d, according to Kpler.

One major exception to the decline was Iraq, which sent 295,000 bbl/d to the United States, up by 140,000 bbl/d from November. Shipments from Venezuela increased 22,738 bbl/d.

Booming U.S. shale production and growing stockpiles also crimped the nation's appetite for imported crude. U.S. commercial crude stocks rose to 441 MMbbl in the week ended Dec. 21, up from 394 MMbbl in mid-September, according to the U.S. Energy Information Administration.

"When inventories began rising, that started to help decrease the demand for imports," said Gene McGillian, vice president of market research at Tradition Energy in Stamford, Connecticut. "We could see even lower imports from OPEC."

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