Washington's decision not to renew the exemptions granted to countries buying Iranian crude oil came into force on Thursday as part of tougher US sanctions on Tehran over its nuclear program and interference in the region's affairs. 

On April 22, the United States demanded that countries buying Iranian oil stop importing it by May 1, or face the prospect of sanctions.

The six-month deadline, granted by the United States to eight countries, mostly in Asia, ended in order to stop importing Iranian oil, whose revenues Tehran is using to finance destabilizing activities in the region. 

The United States hopes US oil production, which reached its highest level in history, will provide oil markets with a need to keep prices low. 

According to sources close to the administration, National Security Adviser John Bolton and Energy Secretary Rick Perry played a major role in persuading US President Donald Trump that it was time to stop Iran's oil exports altogether. 

The sources said that some of the staff of the State Department expressed concern that the price of oil may rise after the decision, but they were convinced after that, and supported a tough policy towards Iran.

With the start of non-renewal of exemptions for Iran's crude oil buyers, US special envoy to Iran Brian Hawk will hold meetings at the UN headquarters in New York to brief the permanent members of the Security Council on the latest developments in US policy towards Iran. 

During his meetings, Hawk will stress the importance of holding Iran accountable for defying Security Council resolutions by developing and testing ballistic missiles, the State Department said. 

Hawk will also stress the need to implement all international resolutions on Iran, including restricting the travel of its officials and banning the purchase of arms, the ministry said.