US President Barack Obama hit out at conservative Republicans, warning he would not negotiate on raising the debt ceiling in a showdown that threatens to throw the government into default.

Obama said in an interview broadcast Sunday that he was willing to talk to Republicans on the separate task of agreeing on a budget, but would not allow conditions to be attached to increasing the government's borrowing limit.

If no deals are reached in bitterly divided Washington, the US government could be shut down by the beginning of October and the United States could begin defaulting on its debts by the middle of next month.

Conservative House Republicans are determined to use the showdown about raising the government's $16.7 trillion debt limit as a way to defund Obama's national health care law.

"What I haven't been willing to negotiate, and I will not negotiate, is on the debt ceiling," Obama said in an interview with the ABC News Show "This Week."

"If you take a look, what has never happened in the past was the notion that-- in exchange for-- fulfilling the full faith and credit of the United States, that we are wiping away, let's say major legislation, like the Health Care Bill."

Obama said that it was unacceptable to establish a precedent for his administration and for future presidents that periodical debates on raising the debt ceiling could be used as levers by some political groups to radically reshape the structure of the US government.

Obama said that a wider problem in US politics was that a group of Republicans was determined to thwart him, whatever he did.

"We have a faction of the Republican Party in the House of Representatives in particular, that view 'compromise' as a dirty word, and anything that is even remotely associated with me, they feel obliged to oppose," Obama said.

"My argument to them is real simple. That's not why the people sent you here."

Obama said that he was willing to negotiate with Republicans on framing an operating budget for the government -- but again suggested his opponents in the House were not sincere in their negotiating position.

The president also offered to talk to Republicans about a way to erase automatic budget cuts that came into force earlier this year after the two sides failed to agree a deficit reduction deal.

"There are ways of doing this, it's just that they haven't been willing to negotiate in a serious way on that," Obama said.