People look at the job listings posted at an unemployment office in San Juan, Puerto Rico.

"The economic security and well-being of 3.5 million Americans living in the commonwealth is at stake," Antonio Weiss, a counselor to Treasury Secretary Jack Lew, said at a hearing at the Senate Committee on Energy and Natural Resources. "I can tell you with total confidence that Puerto Rico's fiscal crisis is escalating and is very real, and that without federal action it could easily become a humanitarian crisis as well."

Puerto Rico's fiscal problems could turn into a humanitarian crisis, a top U.S. Treasury official warned on Thursday.

Weiss called for legislators to help the struggling island, saying that administrative authorities are "simply insufficient" to end the crisis.

The U.S. Treasury had urged Congress on Wednesday to help debt-stricken Puerto Rico, saying the U.S. commonwealth needs the ability to file for bankruptcy protection, changes to Medicaid funding and access to the Earned Income Tax Credit.

"Only Congress has the authority to provide Puerto Rico with the necessary tools to address its near-term challenges and promote long-term growth," Treasury said in a statement.

Read MoreHow can Puerto Rico get out of this 'mess'?



Puerto Rico, a U.S. territory home to 3.5 million, is buckling under $72 billion in debt and a 45 percent poverty rate. With financial creditors resisting reductions to debt payments and political gridlock threatening proposed spending reforms, some Puerto Rican leaders have called on the U.S. government to step in.

"Without federal action, this crisis will escalate and result in further economic contraction, out-migration and suffering of American citizens in Puerto Rico," Weiss said.

—Reuters contributed to this report.