The U.S. sharply tightened energy sanctions against Iran on Thursday, seeking to cut the Islamic Republic’s exports to zero and ushering in a new era of uncertainty for the oil market, notes CNBC.

Last week, the Trump administration surprised the market by announcing it would not extend the waivers which were granted to eight nations last year, allowing them to import limited quantities of Iranian crude. 

Investors and analysts expected Trump to tighten the waivers every six months, allowing China, India, Turkey and other importers to gradually wind down purchases of Iranian crude.

The surprise move to cut off Iran’s exports threatens to wipe out much of the shipments, which have recently totaled more than 1 million barrels per day, or roughly 1% of global consumption. To fill that gap and prevent fuel costs from spiking, Trump has turned to Saudi Arabia, the world’s top oil exporter.

But the Saudis have not made firm commitments and continue to consider extending a six-month agreement to limit crude production with OPEC nations and allied oil producers.

That is raising concerns about a period of tighter supply and higher oil prices.