Oil climbed above $80 a barrel on Thursday as tightening supplies and strong demand took prices back to the highest levels in almost four years. Iran is in focus after the US withdrew from the nuclear deal and reimposed sanctions against the country’s oil exports. Meanwhile, Venezuela’s oil supplies have dropped as political and economic crises take hold of the energy sector. Prices have escalated over the past year as supply cuts led by Opec and Russia have coincided with robust demand, helped by a stronger global economy, and geopolitical upheavals around the world.

Brent crude, the international benchmark, rose to a high of $80.18 a barrel, while West Texas Intermediate, the US marker, increased to $72.30 a barrel. Recommended Energy Source The week in energy: Iran and the oil price Swelling supplies from US shale fields to 10.7m barrels a day were expected to fill any gap in global supplies, but the industry has faced infrastructure bottlenecks and other limitations.

Some industry analysts have in recent days even called for a return to $100 a barrel. Saudi Arabia, Opec’s de facto leader, has said it will work with other producers to alleviate any supply shortages if needed. This has spurred questions about when global producers will exit the supply cut deal in place since 2017. The International Energy Agency on Wednesday warned that a surge in prices would curtail global oil demand growth this year, from 1.5m barrels a day to 1.4m b/d.