Oil markets are tightening with a recent surplus draining, trade figures show. The volume of unsold crude stored in the Atlantic basin has dwindled from around 30 cargoes to just a handful in recent weeks, a Reuters analysis showed.
"The contracts are in a strong up-trend," said Robin Bieber, who watches price charts for brokerage PVM Oil Associates.
Investors are worried that, with Venezuelan supply falling sharply, Iranian crude supply will be cut sharply ahead of the imposition on U.S. sanctions on Tehran in November.
"The November deadline to comply with the U.S. demands for an Iran oil embargo is moving closer, and in anticipation, buyers seemingly have begun reducing their purchases," said Norbert Ruecker, commodity analyst at Swiss bank Julius Baer.
"Venezuela remains equally concerning," he added.
U.S. President Donald Trump threatened in an interview with Bloomberg News on Thursday to withdraw from the World Trade Organization, his latest salvo in a deepening dispute between the United States and its major trading partners.
Economists are worried that rising trade barriers between the world's major economies will drag on global growth and, by extension, erode energy demand.