Efforts by the US and its allies to cripple the Taliban's sophisticated financial network in Afghanistan have barely made a dent, the New York Times reported on Monday citing unnamed American officials. The Taliban in Afghanistan are running a sophisticated financial network to pay for their insurgent operations, raising hundreds of millions of dollars from the illicit drug trade, kidnappings, extortion and foreign donations that American officials say they are struggling to cut off, the influential US daily said. In Afghanistan, the Taliban have imposed an elaborate system to tax the cultivation, processing and shipment of opium, as well as other crops like wheat grown in the territory they control, it said citing American and Afghan officials. In the Middle East, Taliban leaders have sent fund-raisers to Arab countries to keep the insurgency's coffers brimming with cash. Estimates of the Taliban's annual revenue vary widely. Proceeds from the illicit drug trade alone range from $70 million to $400 million a year, according to Pentagon and United Nations officials cited by the Times. By diversifying their revenue stream beyond opium, the Taliban are frustrating American and NATO efforts to weaken the insurgency by cutting off its economic lifelines, the officials were quoted as saying. "Despite efforts by the United States and its allies in the last year to cripple the Taliban's financing, using the military and intelligence, American officials acknowledge they barely made a dent," the Times said. The Times cited American officials as saying that they have been surprised to learn in recent months that foreign donations, rather than opium, are the single largest source of cash for the Taliban. The CIA recently estimated in a classified report that Taliban leaders and their associates had received $106 million in the past year from donors outside Afghanistan, a figure first reported last month by The Washington Post. Private citizens from Saudi Arabia, Pakistan, Iran and some Persian Gulf nations are the largest individual contributors, an American counter-terrorism official cited by the Times said. Top American intelligence officials and diplomats say there is no evidence so far that the governments of Saudi Arabia, the United Arab Emirates or other Persian Gulf states are providing direct aid to the Afghan insurgency. But American intelligence officials cited by the Times say they suspect that Pakistani intelligence operatives continue to give some financial aid to the Afghan Taliban, a practice the Pakistani government denies. The Times cited American officials as saying they are working closely with the Afghan government to dry up the Taliban financing but, as one senior American military officer in Afghanistan put it last week, "I won't overstate the progress."