Congress plunged the U.S. government into a partial shutdown Tuesday for the first time in nearly two decades, as a conservative attempt to derail President Barack Obama's health care overhaul stalled a temporary funding bill.
About 800,000 federal workers are being forced off the job and most nonessential federal programs and services are being suspended, including national parks, museums in Washington and agencies like NASA and the Environmental Protection Agency.
It wasn't clear how long the standoff would last, but there were no signs of compromise. The Senate prepared to convene Tuesday morning, certain to reject the Republican-controlled House's latest version of the funding bill, which would delay key portions of the health care law.
Stock markets around the world were reacting resiliently, with analysts saying significant damage to the U.S. economy was unlikely unless the shutdown lasted more than a few days. U.S. stock futures rose Tuesday, while European stocks mostly recovered after falling the day before the shutdown deadline. Asian stocks were mixed.
The stand-off pits Democrats against a core of conservative activists who have mounted a campaign to seize the must-do budget measure in an effort to derail the 2010 health care reform, which is intended to provide coverage for the millions of Americans now uninsured.
Republicans passionately oppose the plan they have dubbed "Obamacare" as wasteful and restricting freedom by requiring most Americans to have health insurance.
A key part of the health law was taking effect Tuesday, unaffected by the shutdown. Enrollment opened for millions of people shopping for medical insurance.
Also exempt from the shutdown were people classified as essential government employees, including air traffic controllers, Border Patrol agents and most food inspectors.
Pentagon and administration lawyers were looking for ways to expand the number of Defense Department civilians who are exempt from furloughs, amid worries that that the shutdown is damaging U.S. credibility among its international allies, Defense Secretary Chuck Hagel said Tuesday.
"It cuts straight to the obvious question: Can you rely on the United States as a reliable partner to fulfill its commitments to its allies?" Hagel told reporters traveling with him to South Korea.
Until now, such temporary spending bills have been routinely passed with bipartisan support, ever since a pair of unpopular shutdowns 17 years ago severely damaged Republican election prospects and revived then-President Bill Clinton's political standing.
Obama accused Republicans of holding the budget hostage to get what they want.
"You don't get to extract a ransom for doing your job, for doing what you're supposed to be doing anyway, or just because there's a law there that you don't like," Obama said Monday, delivering a similar message in private phone calls later to Republican House Speaker John Boehner and other lawmakers.
Boehner said he didn't want a government shutdown, but he insisted that the health care law "is having a devastating impact. ... Something has to be done."
Republican leaders have voiced reservations about the effort and many lawmakers predicted it wouldn't work, fearing the public will blame their party for the shutdown. But individual Republican House members may face a greater risk by embracing a compromise. Many represent heavily partisan congressional districts, and voters in Republican primaries have ousted lawmakers they see as too moderate.
It appeared for now that the Democrats had the upper hand.
"We can't win," said Republican Sen. John McCain, adding that "sooner or later" the House would have to agree to Democrats' demands for a simple, straightforward funding bill reopening the government.
The military will be paid under legislation freshly signed by Obama, but paychecks for other federal workers will be withheld until the impasse is broken. Federal workers were told to report to their jobs for a half-day but to perform only shutdown tasks like changing email greetings and closing down agencies' Internet sites.
The self-funded Postal Service will continue to operate and the government will continue to pay retirement benefits and health benefits for the poor and elderly.
The State Department will continue processing foreign applications for visas. Embassies and consulates overseas will continue to provide services to American citizens.
The underlying spending bill would fund the government through Nov. 15 if the Senate gets its way or until Dec. 15 if the House does.
Republicans are likely to take up the health care fight again when Congress must pass a measure to increase the borrowing cap, which is expected to hit its $16.7 trillion ceiling in mid-October.
Obama has vowed not to negotiate over the debt ceiling, noting that a default would be worse for the economy than a partial government shutdown. The U.S. risks a market-rattling, first-ever default on its obligations if Congress fails to raise that limit.