US Shutdown Is 'Ideological Crusade' - Obama
President Barack Obama has urged Republicans in Congress to reopen the government, saying "one faction of one party" does not get to "hold the economy hostage over an ideological crusade".
Speaking from the White House Rose Garden more than 12 hours into a government shutdown, Mr Obama said the longer an impasse continues, the worse the impact will be.
America woke up to the shutdown after a deeply polarised Congress failed to agree a new budget in a dispute over Mr Obama's signature healthcare law.
The president said shutting down the government will not accomplish some Republicans' stated goal of "rolling back efforts to provide health insurance for those who don't have it".
Earlier Tuesday, Mr Obama sent federal workers a letter lamenting that they had become "punching bags" in Washington's partisan fiscal fights.
"This shutdown was completely preventable. It should not have happened," Mr Obama said in the letter.
As the shutdown entered into force, "closed" signs and barricades sprang up at the Lincoln Memorial, museums and federal workplaces across the country.
Some of America's most famous tourist attractions, such as the Statue of Liberty and Ellis Island in New York, and Alcatraz Island near San Francisco were closed to the public.
Almost all of Nasa shut down, except for Mission Control in Houston. Even the National Zoo's popular panda cam went dark, shut off for the first time since a cub was born there in late August.
Up to 800,000 government employees are furloughed, and more than a million others could be asked to work without pay.
Meanwhile, workers classified as essential government employees, such as air traffic controllers or Border Patrol agents, continue to work.
Republicans in the House said on Tuesday they would push for a series of small funding bills aimed at reopening portions of the government, including national parks.
The White House rejected the plan, saying it showed an "utter lack of seriousness" on funding the federal government.
The government's return to full operation will depend on how long it takes politicians to bridge their differences - and there was no immediate sign of compromise on Capitol Hill.
For now, Democrats and Republicans keep blaming each other.
The Republicans had insisted on delaying the healthcare reform - dubbed Obamacare - as a condition for passing a bill.
But this approach was rejected by allies of the president in a series of back-and-forth moves between the Republican-controlled House and the Democrat-dominated Senate.
The Democrats accused the Republicans of succumbing to the Tea Party hard-line conservatives and seeking to gain political advantage at the expense of citizens.
Senate Majority Leader Harry Reid said: "The government is closed because of the irrationality of what's going on on the other side of the Capitol."
House Speaker John Boehner, a Republican, said he did not want a government shutdown, but added the healthcare law "is having a devastating impact ... Something has to be done."
Meanwhile, Obamacare itself was unaffected and enrolment opened for millions of people shopping for medical insurance.
Online insurance marketplaces at the heart of the healthcare overhaul struggled to handle the volume of consumers on Tuesday, resulting in some glitches.
The shutdown, meanwhile, is likely to further alienate citizens already largely disillusioned by their ruling class and for the most part disappointed with the president's performance, according to the latest polls.
The political dysfunction on Capitol Hill also raised fresh concerns about whether Congress can meet a crucial mid-October deadline to raise the government's $16.7trn debt ceiling.
This would force the country to default on its obligations, dealing a potentially painful blow to the economy and sending shockwaves around global markets.