"The competing demands on their time from their professional and advocacy lives sometimes make it difficult for high-profile individuals to carry out a formal United Nations role," he said. As a messenger of peace, Clooney traveled to Democratic Republic of Congo and South Sudan. Dujarric said UN Secretary-General Ban Ki-moon hoped there would be future opportunities for collaboration between Clooney and the United Nations. In 2010, Clooney helped found the Satellite Sentinel Project, which tracks human rights abuses and mass atrocities in Sudan. READ: GEORGE CLOONEY GETS ENGAGED"Retiring from his UN role will afford him the independence to move forward with this and other personal advocacy projects and activities," Dujarric said. When Clooney was named a UN Messenger of Peace in 2008, Ban cited his work on raising awareness about violence in Sudan's conflict-torn western Darfur region, where he advocated for aid for the millions of people displaced by fighting.