A plan to squelch the trade in diamonds used to fund civil wars in Africa does not contain strict enough controls, a U.S. congressional agency says. The General Accounting Office, the investigative branch of the U.S. Congress, on Tuesday said the plan, known as the Kimberley Process, relies too heavily on voluntary participation and does not pay sufficient attention to high-risk areas of Africa, the Associated Press reports. Representatives of the diamond industry, human rights groups and 37 governments are involved in the Kimberley Process. Its aim is to have an international certification plan in place by the end of the year. “Although the Kimberley Process participants have achieved significant cooperation among industry, nongovernmental organizations and governments to address the trade in conflict diamonds,” the GAO report said, “our work suggests that participants face considerable challenges in establishing a system that will effectively deter this trade.” The report recommended that Secretary of State Colin Powell work toward incorporating better controls in the certification plan, the AP reported. In its reply to GAO, the State Department said the agency focused on accountability measures rather than the political achievements made so far, the AP reported. The department recognized the need for improvements but did not think it was possible to achieve them before the plan went into effect. The plan developed by participants in the Kimberley Process will require that diamonds traded internationally come with documentation proving their origin and legitimacy. It’s estimated that conflict diamonds make up about 3% of the annual global diamond trade, said to be worth about $7 billion a year. The profits are said to have paid for weapons and equipment that have prolonged bloody uprisings in places like Sierra Leone.