From the Guardian:
Mr Ahmadinejad’s decree forced all state-owned and private banks to slash borrowing rates to 12%. Inflation is officially 15% but is generally believed to be much higher. State banks had been offering rates of 14%, while those in the private sector ranged from 17% to 28%.[...]
Another economist, Saeed Leylaz, claimed the move was a reward to powerful groups who had supported Mr Ahmadinejad. “I believe the president knows the consequence of this decision but he doesn’t care about the future.”
Let’s see, Iran is 3-8 years away from having the bomb, according to the IAEA…and it’s president doesn’t care about the future. That’s going to drive some discomfort among American hawks.
Although, perhaps domestic unrest in Iran might be a simpler explanation for Ahmadinejad’s move.