Mohsen Hashemi, who is the son of former President Ali Akbar Hashemi Rafsanjani, had been urging Ahmadinejad for months to release $1 billion of Parliament-approved cash to expand the network, while the president himself has made no secret of his desire to bring the Metro, along with its public prestige and valuable construction contracts, under his direct control.

In his resignation letter, Hashemi blamed Ahmadinejad’s government for starving the network of cash and said financial sanctions imposed over Iran’s nuclear program meant the Metro was unable to raise its own funds.

In a declaration that appeared to have sparked Hashemi’s resignation, a state transport official said on Friday that Metro fares would be halved to 1,500 rials (around $0.15) if the government took over.