Pakistan ? Pakistan’s main spy agency continues to arm and train the Taliban and is even represented on the group’s leadership council despite U.S. pressure to sever ties and billions in aid to combat the militants, a research report concluded.

The findings could heighten tension between the neighboring countries and raise further questions about U.S. success in Afghanistan since Pakistani cooperation is seen as key to defeating the Taliban, which seized power in Kabul in the 1990s with Islamabad’s support.

U.S. officials have suggested in the past that current or former members of Pakistan’s powerful Inter-Services Intelligence agency, or ISI, have maintained links to the Taliban despite the government’s decision to denounce the group in 2001 under U.S. pressure.