The missed payment will mark the first default by the commonwealth and shows the depth of the island's economic and cash flow problems. Puerto Rico Gov. Alejandro Garcia Padilla shocked investors in June when he said the island's debt, totaling $72 billion, was unpayable and required restructuring.

According to a 2014 bond offering statement, Puerto Rico has never defaulted on the payment of principal or interest of debt.

"Tomorrow is Aug. 1 and we don't have the money," Victor Suarez, chief of staff for Puerto Rico's governor, told journalists in San Juan, referring to a $58 million payment due on Public Finance Corporation (PFC) bonds.

"The PFC payment will not be made this weekend," Suarez said. "It was not consigned."