BRUSSELS — A top U.S. military official in Afghanistan says a major restructuring is under way to bring virtually all American forces in that country under NATO command.

Vice Adm. Greg Smith says the move will integrate almost all of the 20,000 U.S. troops serving in eastern Afghanistan under Operation Enduring Freedom into the 90,000-strong NATO-led International Security Assistance Force.

Smith said Tuesday that Gen. Stanley McChrystal, the top NATO and U.S. commander in Afghanistan who leads both forces, wants to bring “unity of command” to the war and avoid having allied elements working at cross-purposes.

Smith says once the reorganization is carried out only small special forces detachments and a detention unit will remain outside the NATO command structure.