By Sadeq Saba
BBC Iranian affairs analyst
New petrol rations introduced by Iran's government are the most unpopular policy that a populist leader such as President Mahmoud Ahmadinejad could have implemented.
Iran relies on imports for about 40% of its domestic petrol use
Petrol rationing is a highly sensitive issue because it affects the lives of the millions of low-income people who brought him to power two years ago.
Mr Ahmadinejad resisted introducing this policy for months but it appears that the Iranian parliament finally forced him to do so.
This could indeed turn out to be a turning point for Mr Ahmadinejad's presidency - especially for his nuclear policy.
The millions of Iranians who will be affected by petrol rationing might now blame Mr Ahmadinejad's confrontational foreign policy for their hardship
The government has taken this measure mainly because it feels that Iran could be targeted for sanctions if the nuclear dispute with the international community continues.
Iran depends on international supplies for its fuel, importing about 40% of its petrol.
The millions of Iranians who will be affected by petrol rationing might now blame Mr Ahmadinejad's confrontational foreign policy for their hardship.
It appears that his nuclear programme is still popular with Iranians, but analysts say some might soon ask whether it is worthwhile to make such huge sacrifices for a programme that will not be beneficial to them - at least in the short term.