Brent futures settled down 14 cents, or 0.22%, at $64.25 per barrel, after gaining about 3% last week on news that OPEC and its allies would deepen output cuts.
West Texas Intermediate oil futures were down 17 cents, or 0.24%, at $59.02 a barrel, having risen about 7% last week on the prospects for lower production from OPEC+, which is made up of the Organization of the Petroleum Exporting Countries and associated producers including Russia.
Monday's sudden chill came after customs data released on Sunday showed exports from China in November fell 1.1% from a year earlier, confounding expectations for a 1% rise in a Reuters poll.
"That China trade data is a factor, certainly," said John Kilduff, a partner at Again Capital.
Washington and Beijing have been trying to agree on a trade deal that will end tit-for-tat tariffs, but talks have dragged on for months.
"We're coming up to a bit of a precipice, with the potential for new tariffs to be slapped on Sunday, so this is going to be an intense week," Kilduff said. Additional tariffs could weigh on the demand outlook for crude, he added.
Beijing hopes an agreement with the United States can be reached as soon as possible, China's assistant commerce minister, Ren Hongbin, said on Monday.Monday's declines also went against signs on Friday that China was easing its stance on resolving the trade dispute with the United States, confirming it was waiving import tariffs for some soybean and pork shipments.
The price drop also put an end to a strong run in previous sessions fuelled by hopes for the OPEC+ production curb deal.
On Friday, OPEC+ agreed to deepen its output cuts from 1.2 million barrels per day (bpd) to 1.7 million bpd, representing about 1.7% of global production.
"This decision crystallises an important shift in strategy to managing short-term physical imbalances rather than trying to correct perceived long-term imbalances through open-ended commitments," Goldman Sachs said in a note.
The bank revised its Brent spot price forecast to $63 per barrel for 2020, up from a previous estimate of $60.
BofA Merrill Lynch said in a note that strong compliance with the OPEC+ along with positive economic developments such as a U.S.-China trade deal could push Brent to $70 a barrel before the second quarter of 2020.
(Reporting by Jessica Resnick-Ault in New York; Additional reporting by Aaron Sheldrick in Tokyo and Noah Browning in London; Editing by Lisa Shumaker and Matthew Lewis)
By Jessica Resnick-Ault