Oil prices rose on Monday as United States sanctions against Iran’s fuel exports began but were softened by waivers allowing major buyers to import Iranian crude for a while.

Tehran said that it would defy Washington and continue to sell.

Brent crude oil was at $72.83 a barrel by 1230 GMT while US light crude was 15 cents lower at $62.99.

At 2.00 a.m. commodities, US crude was $62.91 per barrel and Brent was last at $72.62.

At 3.00 a.m. US crude was $62.68/barrel while Brent was last at $72.41.

“Oil bulls have long pinned their hopes on the Iran factor and today’s dearth of upside potential will be a major source of concern,’’ Stephen Brennock, an analyst at brokerage PVM Oil, said.

Washington imposed sanctions against Iran on Monday, restoring measures lifted under a 2015 nuclear deal negotiated by the administration of former US President Barack Obama.

In response, Iranian President Hassan Rouhani said, in a speech broadcast on state Media that Iran would break the sanctions and continue to sell oil.