Opium poppy cultivation levels in Afghanistan are at a record high, though the U.S. government has spent over $7 billion to stop it, a federal watchdog states in a new report.

In a letter to Secretary of State John Kerry, Secretary of Defense Chuck Hagel, Attorney General Eric Holder and US AID head Rajiv Shah, Special Inspector General for Afghanistan Reconstruction (SIGAR) John F. Sopko writes: “Despite spending over $7 billion to combat opium poppy cultivation and to develop the Afghan government’s counternarcotics capacity, opium poppy cultivation levels in Afghanistan hit an all-time high in 2013.”

“As of June 30, 2014, the United States has spent approximately $7.6 billion on counternarcotics efforts in Afghanistan,” the letter states.

“Despite the significant financial expenditure, opium poppy cultivation has far exceeded previous records,” he writes, adding that this “calls into question the long-term effectiveness and sustainability of those prior efforts.”

The value of opium and opium-made products in Afghanistan—the world’s largest producer of opium—rose 50 percent from 2012 to 2013, the report states, citing United Nations Office on Drugs and Crime (UNODC) figures.

Though the crop has funded extremist and criminal groups and contributed to a public health crisis, many Afghans see opium poppy cultivation as their only option. A UNODC report issued last year stated that Afghan farmers cited as among the top reasons for their cultivation of opium poppy its high sales price, high income from little land, improving their living conditions, and poverty.