The debt, now $293 million, is projected to reach $478 million by the end of the year, based on data from the State Department and the Senate appropriations subcommittee overseeing it, USA Today said Thursday.

One delinquent account is the U.N. peacekeeping office, which is owed nearly $160 million on obligations dating back to 2005, the data show. The past-due amount likely will grow to $266 million this year.

Since early 2007, the United States has fallen into arrears of $51million in dues to the regular U.N. budget, the newspaper said. 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," Sen. Patrick Leahy, D-Vt., told USA Today in a statement, "and for years, our support has fallen short. Joint efforts through (such groups) cost us far less ... and can also be more effective."

President George Bush's 2009 budget plan would apply $50 million toward the debt.