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Opium poppy cultivation has hit an all-time high in Afghanistan despite a 10-year, $7.6 billion effort by the U.S. government to fight it, according to a new report.

The Special Inspector General for Afghanistan, who authored the report, warned Secretary of State John Kerry, Attorney General Eric Holder and other top U.S. officials that the gap between expenditures and results should make them rethink their approach.

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"Given the severity of the opium problem and its potential to undermine U.S. objectives in Afghanistan," said Special Inspector General John Sopko in a letter to the officials, "I strong suggest that your departments consider the trends in opium cultivation and the effectiveness of past counternarcotics efforts when planning future initiatives."

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According to SIGAR's report, the value of the opium produced in Afghanistan reached $3 billion in 2013, a 50 percent increase from 2012, and is likely to increase still further in 2014. Some of the increase is due to the use of affordable “deep well” technology over the past decade to turn 200,000 hectares of former desert in southwestern Afghanistan into arable land. Some of the land is now being used to grow opium poppies.

Opium poppy cultivation is used to fund the Taliban and other insurgent groups and stokes corruption, says the report.

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