A sovereign state, Croatia is a republic governed under a parliamentary system. It is a member of the European Union, the United Nations, the Council of Europe, NATO, the World Trade Organization, and a founding member of the Union for the Mediterranean. An active participant in United Nations peacekeeping, Croatia has contributed troops to the International Security Assistance Force and took a nonpermanent seat on the United Nations Security Council for the 2008–2009 term. Since 2000, the Croatian government has invested in infrastructure, especially transport routes and facilities along the Pan-European corridors.