The US government has shut down after Congress failed to pass a key budgetary measure on time.
Lawmakers had hoped to approve a new spending bill before federal funding expired at midnight.
But Republican Senator Rand Paul ended hopes for a quick vote when he demanded a debate in the chamber on his amendment to maintain spending caps.
In January, a similar failure to pass a bill led to a three-day government shutdown.
The federal Office of Personnel Management said government operations would “vary by agency.”
Both the Senate and the House of Representatives need to approve the new two-year spending deal.