- US government currently runs a $1.5tn budget deficit, requiring it to issue debt in the form of treasury bills, bonds and other securities
- Public debt was $14.3tn on 31 May, up from $10.6tn when Mr Obama took office in January 2009
- Most is held by the public, with the rest held in US government accounts
- Congress has voted to raise the US debt limit 10 times since 2001
Failure to raise the US debt ceiling could trigger another recession and throw millions out of work, President Barack Obama has said.Mr Obama is struggling to marshal support for a budget package that would include some $4tn (£2.5tn) of cuts.
But ahead of renewed budget talks with Republicans on Monday, Mr Obama said the stalemate would be resolved within a "reasonable period of time".
The US risks defaulting on its debts on 2 August, when the budget runs out.
Speaking before meeting with Republicans over the nation's federal budget, Mr Obama said it would be "not acceptable" for lawmakers to fail to raise the US debt ceiling.
"We don't risk US default on our obligations because we can't put politics aside," the president said.
But Mr Obama said there would be no deal on raising the government's debt limit if Republicans would not compromise.
"I don't see a path to a deal if they don't budge. Period," the president said, adding that a stop-gap resolution to the budget stalemate would not be considered.
"I will not sign a 30-day, or 60-day or 90-day extension," the president said.
Republicans are opposing the Obama proposals because they include plans for some tax rises. And his Democratic allies are no more enthusiastic about proposals to cut social welfare and Medicaid.
After talks on Sunday ended with no resolution, Mr Obama said he would call for daily meetings until the stalemate over the budget is broken.
"We are going to get this done by 2 August," he told reporters.
The US currently runs an estimated $1.5 trillion (£932bn) annual budget deficit, and has already exceeded the national debt limit of $14.3tn.
The government's borrowing authority is limited by statute.
'Taking on heat' On Monday, President Obama criticised politicians who have said the debt ceiling does not need to be raised.
US federal government debt
"It's irresponsible. They know better," Mr Obama said.The president added that he was "prepared to take on significant heat from my party to get something done".
Mr Obama also said Republican Speaker of the House of Representatives, John Boehner, faced a potential revolt from his caucus if a deal was not made before the 2 August deadline.
The president added that Republicans should take a political risk by "taking on their sacred cows", something the Democratic president said he was willing to do.
"I am prepared to take on significant heat from my party to get something done," Mr Obama said.
'Bigger savings' On Sunday, eight top Senate and House of Representatives leaders met at the White House.
Mr Boehner said on Saturday that he favoured a less ambitious target for debt reduction of $2tn.
White House aides have previously insisted Mr Obama would hold out for bigger savings, and Treasury Secretary Timothy Geithner has also insisted that the deadline for a deal could not be extended.
When it came to the crunch in the past Congress regularly voted to raise the debt ceiling, giving government access to the cash it needed.
This year, however, newly-empowered Republicans are determined to prevent any tax increases and want to see aggressive measures to reduce the deficit in exchange for agreeing to raise the debt ceiling.
A group of Republican and Democratic members of Congress led by Mr Biden had identified about $2tn in cuts in talks over May and June but those ended in an impasse.
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