Puerto Rico's transit system shutdown, which is planned for Monday, will jeopardize its funding from the United States, the Department of Transportation warned Friday.

Reuters reported the island's debt crisis could escalate with the shutdown's effects after lawmakers were unable to agree on a 68 percent increase in oil tax.

The tax hike would have backed a bond sale of up to $2.9 billion and helped to pay salaries, which the local department will not be able to do as of Monday, according to Businessweek.

The local union is coaxing workers of the buses and the suburban Tren Urbano to work as scheduled on Monday. About 75,000 people use the public transportation daily. 

The U.S. government provides billions of dollars annually to the island territory for grants for transport projects, health care and social security, Reuters reported.

Federal Highway Administration and the Federal Transit Administration warned Miguel Torres, Puerto Rico's transport secretary, that the shutdown would be a breach of commitment to maintain basic levels of operations for safety and security, Retuers reported.

 "Failure to fulfill these capacity obligations or your responsibility to properly protect federal assets could jeopardize future federal funding or potentially result in a debt to the federal government," the FTA said in a letter dated Wednesday, Nov. 26, Reuters reported.

But Torres said that his department has already done as much as they can on its end to help curb expenses and continue operations.

"We are being forced to make several decisions that unfortunately will have an impact on thousands of public workers," he told Businessweek. "Even then, it's not enough. ... (We're) up against the wall."

U.S. bondholders are increasingly worried about public corporations declaring bankruptcy because of the current debt crisis on the island.

Credit rating agencies have downgraded Puerto Rico's public debt, and none of the public corporations have restructured despite a law approved by Gov. Alejandro Garcia Padilla earlier this year to allow such action.