Brent crude futures fell $1.04, or 1.7%, to $58.88 a barrel. US West Texas Intermediate (WTI) crude futures fell $1.47, or 2.7%, to $53.88 a barrel.
Brent futures were set to gain 0.4% for the week, while WTI was on track to fall 1.9% for the week.
China's commerce ministry said it would impose additional tariffs of 5% or 10% on a total of 5,078 products originating from the United States, including agricultural products such as soybeans, crude oil and small aircraft.
In retaliation, US President Donald Trump said he was ordering US companies to look at ways to close their operations in China and make more of their products in the United States instead.
"We still view the US-Chinese trade standoff as a major bearish consideration that will likely be requiring additional downward oil demand adjustments as this year proceeds," said Jim Ritterbusch, president of Ritterbusch and Associates.
Investors also focused on a speech by US Federal Reserve chair Jerome Powell at an annual economic symposium in Jackson Hole, Wyoming.
The US economy is in a "favorable place" and the Federal Reserve will "act as appropriate" to keep the current economic expansion on track, Powell said.
The remarks gave few clues about whether the central bank will cut interest rates at its next meeting or not.
Meanwhile, St. Louis Federal Reserve Bank President James Bullard said policymakers will have a "robust debate" about cutting US interest rates by half a percentage point at their next policy meeting in September.
Exacerbating concern over the possibility of recession, US manufacturing industries registered their first month of contraction in almost a decade.
"Some have blamed the hesitant tone (for oil prices) on an end-of-summer lull. Yet, in truth, the sense of unease stems from ongoing worries about the global economy," said Stephen Brennock of oil broker PVM.
Tensions in the Middle East have kept investors on edge as well. Iran's foreign minister said talks held on Friday with French President Emmanuel Macron about a landmark 2015 nuclear deal were "productive."
Iran has said it will scale back compliance with the pact unless the Europeans find a solution enabling Tehran to sell its oil despite US sanctions.