The most active global Brent crude contract also ended lower on concerns about vaccine distribution and the efficacy of one vaccine.

"The vaccine numbers are just not there," said Bob Yawger, director of energy futures at Mizuho in New York.

Oil markets have rallied about 50% since October on the back of vaccine rollouts, but the emergence of COVID-19 variants has fanned worries about economic weakness. Yawger said a U.S. economic stimulus package may not come quickly enough to support the market.

U.S. President Joe Biden urged Congress to take swift action on a $1.9 trillion COVID-19 relief proposal.

"There is no time for any delays," Biden said. "It could take a year longer to return to full employment if we don't act and don't act now."

Global benchmark Brent crude futures for March settled up 36 cents, or 0.6% a barrel, at $55.88. The Brent March contract expires on Friday. The more active April contract settled down 6 cents a barrel, at $55.04.

U.S. West Texas Intermediate (WTI) crude futures fell 14 cents, or 0.3%, to $52.20.

Both front-month Brent and WTI were on track to post a weekly gain of less than 1%.

A Reuters poll showed oil prices are expected to hover around current levels for much of 2021 before a recovery gains traction towards year-end.

U.S. crude fell along with stock indexes, as investors gauged the efficacy data of Johnson & Johnson's COVID-19 vaccine. The drugmaker's shares fell after it said its single-dose vaccine was 72% effective in preventing COVID-19 in the United States, with a lower rate of 66% observed globally.

Saudi Arabia is set to cut output by 1 million barrels per day (bpd) in February and March. Compliance with output curbs by the Organization of the Petroleum Exporting Countries and allies, together known as OPEC+, improved in January.

OPEC oil output rose in January, a Reuters survey found, after OPEC+ agreed to an easing of supply curbs.

However, the rise was less than the agreed amount, with an involuntary drop in Nigerian exports limiting the increase.

(Reporting by Jessica Resnick-Ault in New York; Additional reporting by Bozorgmehr Sharafedin in London, Roslan Khasawneh in Singapore and Sonali Paul in Melbourne; Editing by David Goodman, Louise Heavens, David Gregorio and Richard Chang)

By Jessica Resnick-Ault