U.S. President Barack Obama said on Thursday that the government shutdown is not about spending, but solely due to the Republicans' obsession with dismantling his signature health care law.

In a speech at Maryland, Obama said the only thing preventing the federal government from reopening is that House Speaker John Boehner won't hold a yes-or-no vote on a Senate-passed bill because Boehner doesn't want to anger the "extremists" in his party.

"This is not about spending, and this is not about fiscal responsibility. This whole thing is about one thing. The Republican obsessions with dismantling the Affordable Care Act and denying affordable health insurance to millions of Americas," Obama said.

He argued that a government shutdown won't change the fact that millions of Americans need health insurance and that the Affordable Care Act, commonly known as Obamacare, is being implemented. "The shutdown does not change that."

"Congress has to pass a budget that funds our government with no partisan strings attached," he said.

He also warned that as reckless as a government shutdown is, an economic shutdown that results from a debt default would be dramatically worse.

In a Thursday's report on the potential effects of debt ceiling brinksmanship, the Treasury said the economic fallout of a debt default would echo the events of 2008 financial crisis, or even worse.

"Postponing a debt ceiling increase to the very last minute is exactly what our economy does not need -- a self-inflicted wound harming families and businesses. Our nation has worked hard to recover from the 2008 financial crisis, and Congress must act now to lift the debt ceiling before that recovery is put in jeopardy," said Treasury Secretary Jacob Lew.