What Does Iran's Cash Buy in Afghanistan?

Abedin Taherkenareh/European Pressphoto Agency President Hamid Karzai of Afghanistan and Mahmoud Ahmadinejad of Iran at a regional summit in Tehran in August.

President Hamid Karzai of Afghanistan has admitted that Iranian officials are regularly giving his government bags of cash worth millions of dollars, and he makes no apologies for these payments. An article in The Times on Saturday by Dexter Filkins quoted several Afghan officials close to Mr. Karzai as saying that the government used the money to buy the allegiance of Afghan elected officials, tribal leaders and insurgent commanders.

What is Iran getting for its money? Does its financial help influence the Karzai government and generally affect the geopolitical balance in the region? What are Iran's interests in Afghanistan, beyond wanting to challenge the United States? nytimes.com