US lawmakers have failed to avert a partial shutdown of government services after a deadline to agree how federal money should be spent passed without agreement.
The Democrat-dominated Senate and Republican-controlled House of Representatives refused to back down in a clash over President Barack Obama's controversial healthcare law, known as Obamacare.
The deadlock means non-essential services, including some of America's most famous tourist attractions, will be forced to close, while hundreds of thousands of workers face the prospect of being sent home without pay.
It is the first US shutdown in 17 years.
In a frank address to the nation as last-ditch efforts to avoid a shutdown continued, Mr Obama warned such an outcome would have a "very real economic impact, right away".
"The idea of putting progress at risk is the height of irresponsibility," he said.
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