WASHINGTON - The United States federal government shut down for the first time in 17 years on Tuesday, as Congress failed to end a bitter budget row after hours of dizzying brinkmanship.

Ten minutes before midnight, the White House budget office issued an order for many government departments to start closing down, triggering 800,000 furloughs of federal workers, and shutting tourists out of monuments like the Statue of Liberty, national parks and museums.

Prospects for a swift resolution were unclear and economists warned that the struggling U.S. economic recovery could suffer if the shutdown drags on for more than just a few days.

Only workers deemed essential will be at their desks from Tuesday onwards, leaving government departments like the White House with skeletal staff.

Vital functions like mail delivery and air traffic control will continue as normal, however.

On a day of dysfunction and ugly rhetoric in the divided U.S. political system, Republicans had repeatedly tied new government funding to attempts to defund, delay or dismantle President Barack Obama's signature health care law.

But each time their effort was killed by Obama's allies in the Democratic-led Senate, leaving the government in limbo when its money ran out at the end of the fiscal year at midnight Monday.

"This is an unnecessary blow to America," a somber Senate Majority Leader Harry Reid said on the Senate floor two minutes after the witching hour.

A few hours into the shutdown, Republicans in the House appointed delegates, or conferees, to try to negotiate with the Senate later Tuesday on a spending plan to get the government up and running again.

But if they still want to tinker with Obamacare, the Senate will not negotiate, an aide to Reid said.

"If the House follows through with their current plan, the Senate will vote to table the House's conference gambit shortly after convening. And we will be back at square one," the aide said.

Obama, heralding the first government shutdown since 1996, told U.S. troops in a video that they deserved better from Congress, and promised to work to get the government reopened soon.

Sylvia Mathews Burwell, Obama's budget director, said agencies should execute plans for an "orderly shutdown," and urged Congress to swiftly pass bridge financing that would allow the government to open again.

Obama earlier accused Republicans of holding America to ransom with their "extreme" political demands, while his opponents struck back at his party's supposed arrogance.

House Speaker John Boehner rebuked Obama in a fiery floor speech after an unproductive call with the president.

"I didn't come here to shut down the government," Boehner said. "The American people don't want a shutdown, and neither do I."