U.S. and Taliban officials have exchanged proposals for the release of billions of dollars from Afghan central bank reserves held abroad into a trust fund, three sources familiar with the talks said.

Significant differences between the sides remain, however, according to two of the sources, including the Taliban's refusal to replace the bank's top political appointees, one of whom is under U.S. sanctions as are several of the movement's leaders.

While the Taliban do not reject the concept of a trust fund, they oppose a U.S. proposal for third-party control of the fund that would hold and disburse returned reserves, said a Taliban government source who spoke on condition of anonymity.

The U.S. has been in talks with Switzerland and other parties on the creation of a mechanism that would include the trust fund, disbursements from which would be decided with the help of an international board, according to a U.S. source who also declined to be named.