By defaulting tomorrow, Argentina may trigger bondholder claims of as much as $29 billion—equal to all its foreign-currency reserves.

If the overdue interest on Argentina's dollar-denominated securities due 2033 isn't paid by July 30, provisions in bond indentures known as cross-default clauses would allow the nation's other debt holders to also demand their money back immediately. The amount corresponds to Argentina's debt issued in foreign currencies and governed by international laws.

U.S. District Court Judge Thomas Griesa blocked Argentina's attempt last month to transfer the $539 million in interest after the nation didn't set aside money for holdout creditors who won a ruling that entitled them to full repayment of obligations that Argentina repudiated in 2001. While Citigroup Inc. says there's little chance investors will invoke the payback clauses in coming weeks, potential claims are large enough to exhaust the country's reserves.