Guinea has participated in both diplomatic and military efforts to resolve conflicts in Liberia, Sierra Leone, and Guinea-Bissau, and contributed contingents of troops to peacekeeping operations in all three countries as part of ECOMOG, the Military Observer Group of ECOWAS.[2] Guinea has offered asylum to over 700,000 Liberian, Sierra Leonean, and Bissau-Guinean refugees since 1990, despite the economic and environmental costs involved.[citation needed]