Oil prices tumbled on Monday as weak industrial earnings in both China and the United States raised fresh concerns about a global slowdown that could cut fuel demand.

U.S. West Texas Intermediate crude ended Monday's session down $1.70, or 3.2 percent, at $51.99 a barrel, its lowest closing price in two weeks.

Brent crude, the international benchmark for oil prices, was down $1.71, or 2.8 percent, at $59.93 around 2:30 p.m. ET, slipping below $60 for the first time in nearly two weeks.

Profits at Chinese industrial firms contracted in December for a second straight month, China's National Bureau of Statistics said on Monday. The latest datapoint adds to series of weak signals coming from the world's second biggest economy. Last week, Beijing reported that the economy grew at the slowest pace in nearly 30 years in 2018.

Later on Monday, bellwether industrial Caterpillar issued weak guidance for future profits and reported disappointing fourth-quarter earnings, citing the impact of tariffs and slower sales in China.

"Those Caterpillar earnings were sort of a canary in the coal mine in terms of industrial activity out there. Losses sped up after that hit the tape," said John Kilduff, founding partner at energy hedge fund Again Capital.

Kilduff says markets will be closely watching upcoming data from Chinese state run firms and the private manufacturing sector. Also critical will be headlines coming out of the latest trade talks between Washington and Beijing scheduled for later this week, he added.

The ongoing trade dispute — and the threat of higher tariffs on hundreds of billions in goods — is keeping markets on edge.

But despite the trade tension, oil remains on pace for strong gains in January. WTI is up more than 14 percent this month, while Brent is on pace for a gain of about 11 percent.

The price has been supported by early signs that OPEC and its allies are delivering on their pledge to cut production by 1.2 million barrels a day in order to drain oversupply from the market.

Russia, the second biggest contributor to the production cuts, has promised to "pick up the pace," Saudi energy minister Khalid al-Falih told CNBC on Monday. Moscow has said it will throttle back output by 50,000 to 60,000 bpd in January, compared with its goal of cutting 230,000 bpd in the first six months of 2019.