Bloomberg reported on Monday that the Trump administration will not renew U.S. sanctions waivers that let countries buy Iranian oil after they expire on May second. 

The report said U.S. Secretary of State Mike Pompeo plans to announce the decision Monday morning in Washington.

The administration had granted waivers to eight countries — China, Greece, India, Italy, South Korea, Japan, Taiwan and Turkey — for a duration of 180 days when the U.S. reimposed a set of sanctions on Iran last November.

Citing three U.S. officials, the Associated Press reported that the Trump administration may directly warn five countries, including South Korea, of penalties they may incur if they continue to import oil from Iran.

The AP said that since November, three of the eight countries granted exemptions — Italy, Greece and Taiwan — have ceased all Iranian oil imports while the other five have lobbied for waiver extensions. 

Observers say the latest decision is intended to further ramp up pressure on Tehran by curtailing revenue it receives from energy exports.

The news has already jolted markets worldwide. The price of Brent crude rose more than three percent, peaking at over 74 dollars a barrel on Monday, the highest intraday price in almost six months for the global oil benchmark.