OPIUM production in Afghanistan will contribute $US500 million ($770 million) to drug lords and the Taliban this year and has increased in the south - where Australia's troops are based - despite a drop across the rest of the country, a United Nations report says.

The report, to be released today by the UN Office on Drugs and Crime, says opium production has dropped 6 per cent across the country this year and has been eradicated from 18 of 34 provinces. Production has been restricted almost exclusively to the troubled southern provinces, including Oruzgan, where Australia's 1000-plus troops are based and where production rose 26 per cent.

The report says the rises in the south indicate the continued strength of the Taliban which - along with drug lords and corrupt authorities - imposes a tax, or ushr, for protecting opium farmers and traffickers.