Puerto Rico's Governor Alejandro Garcia Padilla could be heading toward a fight with creditors unwilling to take reduced payouts as he tries to restructure the island's $73 billion debt to relieve its fiscal problems.

OppenheimerFunds, with about $4.5 billion exposure to Puerto Rico according to Morningstar, said it believed the island could repay bondholders while providing essential services to citizens and growing the economy. It said it stood ready "to defend the previously agreed to terms in each and every bond indenture."

"We are disheartened that Governor Padilla, in a public forum, has called for negotiations with other creditors, representing and including the millions of individual Americans that hold Puerto Rico municipal bonds," a spokesman for Oppenheimer said in a statement.

Garcia Padilla said on Monday his goal was to come up with a negotiated moratorium with bondholders to postpone debt payments for a number of years.

Puerto Rico's bonds fell sharply for a second session on Tuesday, with general obligation 8 percent bonds maturing in 2035 as low as $64.50 versus a low of $68.75 on Monday. Almost 10 percent of municipal bonds that traded Monday were Puerto Rico-related, according to Janney Capital Markets.

Garcia Padilla's remarks prompted credit rating agencies Standard & Poor's and Fitch to further cut their ratings on the island's bonds. S&P said a default, distressed exchange or redemption of Puerto Rico's debt within the next six months seemed inevitable.

The commonwealth faces a Wednesday deadline on a $655 million payment on general obligation debt. S&P expects the payment to be made.

The island's utility PREPA, with around $9 billion of debt, and creditors have been discussing a deal for the utility to avoid a potential default on $400 million payment due Wednesday, a source familiar with the talks said.

Puerto Rico's deepening financial crisis could speed up an exodus of money from U.S. municipal bond funds.

U.S. open-ended municipal bond funds have $11 billion of Puerto Rico bonds and nearly 53 percent of such funds have exposure to the commonwealth, According to Morningstar. Those with the biggest exposure include Franklin Templeton, Goldman Sachs and MainStay.