Al-Qaeda and its Taliban allies continue to enjoy significant illicit financing from Gulf countries, a senior US Treasury official said Thursday as he reiterated Washington's vow to cut those ties. "We need to redouble our efforts to combat the financial support networks of Al-Qaeda and the Taliban," said David Cohen, Treasury's assistant secretary for terrorist financing. He called financing as essential a part of militant activity as weapons, fighters and extremist ideology. Cohen said the Taliban's January 18 offensive in central Kabul, which included Afghanistan's Central Bank among its targets, is proof that the US policy of hampering the flow of funds to militants was working. Treasury is leading an inter-agency effort to find new ways of combating illicit financial activities in Afghanistan and Pakistan, he said. "The challenge, of course, is to continue to tighten our grip on the Taliban's and Al-Qaeda's financial networks," Cohen added in prepared remarks for a speech to the Council on Foreign Relations think tank. "To some extent, this means sticking to our knitting -- mapping the networks, particularly Gulf-based donors and facilitators." He pointed to the "significant problem of official corruption" in Afghanistan, noting that Treasury was examining how it could address the problem. As part of its bid to disrupt illicit financing, the US government will focus on helping Kabul build its regulatory and law enforcement capacity, Cohen said. Last October, Cohen said that the Taliban's finances likely are in much better shape than those of Al-Qaeda, which have been depleted after years of attacks against the United States and its allies.