President Barack Obama ridiculed House of Representatives Speaker John Boehner on Thursday for refusing to allow a vote on a funding bill that would end a three-day government shutdown, saying the top Republican in Washington is in the grip of conservative "extremists".

Obama's speech at a construction company in the Washington suburb of Rockville, Maryland, showed there was no sign of movement toward a deal that would reopen the government's doors and allow hundreds of thousands of idled government workers to go back to their jobs.

Obama said Republican conservatives in the House are dead set on killing his signature healthcare law and that he is just as adamant at protecting it from being dismantled or defunded.

"This whole thing is about one thing, the Republican obsession with the Affordable Care Act. That seems to be the only thing that unites the Republican Party right now," he said.

Obama called for a straight up-or-down vote on a funding bill that would permit the government to reopen, but said Boehner is intimidated by the most conservative members of the Republican caucus.

Enough Democrats and moderate Republicans would approve the legislation if it came to a vote, said Obama.

"The only thing that is preventing all that from happening right now, today, in the next five minutes, is that Speaker John Boehner won't even let the bill get a yes or no vote because he doesn't want to anger the extremists in his own party. That's all," the president said.

Obama, who had a heated discussion about the shutdown with Boehner and other congressional leaders on Wednesday at the White House, mocked a Republican lawmaker for an eyebrow-raising comment.

"We're not going to be disrespected," Indiana Republican Representative Marlin Stutzman told The Washington Examiner newspaper. "We have to get something out of this. And I don't know what that even is."

Obama said the remark showed what the shutdown drama was about: "This whole thing is about one thing, the Republican obsession with the Affordable Care Act. That seems to be the only thing that unites the Republican Party right now."

Obama said he is willing to negotiate some changes to the law to improve it, but made clear he would not allow the law to be dismantled.

"It's the law of the land, it's here to stay," he said. Congress passed the healthcare law in 2010.

The shutdown battle is a precursor to a more serious fight over raising the US debt ceiling. America's borrowing limit will be reached by October 17 and the United States will be forced into an unprecedented default on its debt if the debt ceiling is not raised.

Obama said a debt default would throw the US economy back into a recession.

"If we screw up, everybody gets screwed up. The whole world will have problems," he said, reiterating that he would not be drawn into negotiations over the debt ceiling.

Obama Blames Republican 'Obsession' For Government Shutdown