Oil prices rose on Friday as concerns over the impact of a trade war depressed sentiment, although impending U.S. sanctions on Iran and falling Venezuelan output supported the market.

Sweet Brent crude oil was  at 77.77 dollars a barrel.

U.S. light crude was at 70.15 dollars.

U.S. President, Donald Trump, threatened on Thursday to withdraw from the World Trade Organisation, his latest salvo in a deepening dispute between the United States and its major trading partners.

Economists worry that rising trade barriers between the world’s major economies will drag on global growth and erode energy demand.

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 the media  analysis showed.

Investors are worried that with Venezuelan supply falling sharply, Iranian crude supply will be cut sharply ahead of the imposition of 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.