WASHINGTON  The United States is hundreds of millions of dollars behind in dues to international organizations ranging from the United Nations peacekeeping office to the agency that sets and enforces global labor standards. The arrears have grown as the United States has fallen short on payments for missions it is obligated to support under international agreements. The debt, at $293 million, is projected to hit $478 million by year's end, based on data from the State Department and the Senate appropriations subcommittee that oversees it. Nearly $160 million is owed for U.N. peacekeeping on obligations dating to 2005, the data show, and that is likely to grow to $266 million this year. Since early 2007, the United States also has fallen into arrears of $51 million in dues to the regular U.N. budget — the first time it hasn't paid all yearly dues in a decade. The rest of the debt is owed to smaller groups, such as the International Labor Organization. The United States relies on the United Nations and other organizations to advance "vital security, economic and humanitarian interests … and for years, our support has fallen short," Sen. Patrick Leahy, D-Vt., told USA TODAY in a statement. "Joint efforts through (such groups) cost us far less … and can also be more effective," said Leahy, chair of the Senate Appropriations subcommittee on foreign operations. Recent budgets haven't covered rising costs for those missions, especially peacekeeping, says George Abrahams of State's Bureau of International Organization Affairs. The United Nations has 17 peacekeeping missions, including a new one in Sudan's Darfur region, he says, and the United States pays 25% of costs. In 2007, the U.S. bill was $1.6 billion; it's likely to hit $2 billion in 2009. Overall U.S. debt to international organizations has risen as the dollar has lost value worldwide, Abrahams says. The debts have not curtailed missions, but they hamper organizations' ability to plan and staff them, says Deborah Derrick of the Better World Campaign, which builds support for U.N. efforts. Many of those missions have grown at U.S. urging, Derrick says. "It's "hypocritical to not fund them fully." Several times since the mid-1990s, Congress has capped U.S. contributions to peacekeeping and other U.N. programs at 25% of their cost, while the United Nations has set dues rates at up to 30%. As a result, the United Nations tallies the U.S. debt well above the $293 million the United States acknowledges. Congress lifted the caps after Democrats took over last year, but recent budgets haven't included money to pay either the acknowledged debts or all current dues. President Bush's 2009 budget plan would put $50 million toward arrears. Withholding dues can help leverage management fixes, says John Bolton, former U.S. ambassador to the United Nations. "Having Congress prepared to do that actually strengthens your … hand in (demanding) reform." Untitled Document International missions come with high price International missions come with high price The United States acknowledges being at least $293 million in arrears on dues payments to international organizations with missions ranging from global peacekeeping to the enforcement of fair labor standards. The debt is projected to grow this year to $478 million. Current arrears include Office Debt Mission Website United Nations peacekeeping mission $159 million Funds and manages U.N. peacekeeping missions worldwide; currently running 17 missions, including those in the Darfur region of Sudan, the Congo and parts of the Middle East. www.un.org United Nations regular dues $51.2 million Global association of governments facilitating cooperation in international law, security, economic development and social equity. www.un.org U.N. Food and Agriculture Organization $9.9 million Leads global efforts to reduce hunger; negotiates international agreements to modernize and improve agriculture, forestry and fisheries practices. www.fao.org International Labor Organization $8.7 million Promotes fair labor standards and equal employment opportunities. www.ilo.org United Nations Educational, Scientific and Cultural Organization (UNESCO) $7.2 million Promotes international cooperation and global standards among U.N. member and non-member states in education, science, culture and communication. www.unesco.org Organization for Economic Cooperation and Development (OECD) $4.5 million Promotes and tracks the spread of democracy and free-market economics; provides international development assistance. www.oecd.org Enlarge By Jim Watson, AFP/Getty Images President Bush shakes hands with Rwandan peacekeepers recently returned from the Darfur region of Sudan before his departure on Air Force One at Kigali International Airport in Kigali on Feb. 19. 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