The U.S. national debt topped $33 trillion for the first time ever on Monday, crossing a critical milestone at a time when government spending is already under scrutiny.

The national debt – which measures what the U.S. owes its creditors — hit $33.04 trillion as of Monday afternoon, according to the latest numbers published by the Treasury Department. By comparison, just four decades ago, the national debt hovered around $907 billion.

"The United States has hit a new milestone that no one will be proud of: our gross national debt just surpassed $33 trillion," said Maya MacGuineas, the president of the Committee for a Responsible Federal Budget. "Debt held by the public, meanwhile, recently surpassed $26 trillion. We are becoming numb to these huge numbers, but it doesn’t make them any less dangerous."

This is a developing story. Please check back for updates.