Four possible stages can be established on the basis of actual or projected developments. Stage 1 is already in existence and covers wide-ranging, formalized, government-sanctioned cooperation. It covers the TREVI working group areas, the cross-Channel Police Intelligence Conferences, Schengen I, a range of bilateral links, and the customs Mutual Assistance Group '92. Stage 2 is the stage of the formal, treaty, or other intergovernmental agreement-based coordination of police, customs, and immigration service work related primarily to the differentiation of controls at the EC's external border as opposed to those at ED internal borders. Stage 3 might be the development of coordination into actual multinational operational units. And Stage 4 is the clear supranational level and might be related either to the FBI or EUROPOLICE, or some merging of the two. This would require considerable political will and political priority on the EC agenda. 14 notes