US President Barack Obama has said that he is willing to negotiate with Republicans on fiscal issues and his signature healthcare law, but warned that "we can't make extortion routine as part of our democracy".

In a press conference at the White House on Tuesday, he urged John Boehner, the House speaker, to hold a vote to end the partial government shutdown and lift the debt ceiling.

The US government has been partially shuttered for more than a week because Congress did not pass a budget before the fiscal year ended on September 30.

As reckless as a government shutdown is, the economic shutdown caused by America defaulting would be dramatically worse.

Barack Obama, US president

Dozens of Republican lawmakers demanded that any budget bill also include provisions to delay implementation of healthcare law, which took effect this month.

Democrats, and a handful of House Republicans, want a "clean" budget bill, without the healthcare changes, and such a bill would probably muster enough votes to pass both houses of Congress. But Boehner has refused to bring it to a vote in the House of Representatives, the lower chamber, because it would create dissent within his Republican ranks.

Responding to Obama's latest comments, Boehner said that the US president's demands amounted to asking for an "unconditional surrender" on the part of Republicans.

Boehner is insisting instead that the two sides start negotiating now on the terms of any budget or debt agreement, saying attaching other measures is a long-held practice.

The US fiscal crisis will become more pronounced in about nine days, when the US government runs out of money to pay its bills. If Congress does not lift the statutory debt ceiling from its current level of $16.7 trillion, the government could default on its debt, sending world financial markets into panic.

"As soon as Congress votes to reopen the government, it's also got to vote to meet our country's commitments, pay our bills, raise the debt ceiling," Obama said. "As reckless as a government shutdown is, the economic shutdown caused by America defaulting would be dramatically worse," he added.

Obama also noted in his news conference that the shutdown already made him cancel a trip to Asia this week. He argued that the crisis is hurting US credibility around the world and "makes it look like we don't have our act together".

Federal reserve appointment

Meanwhile, a White House official said on Tuesday that Obama was due to appoint Janet Yellen as the head of the US Federal Reserve, making her the first female head of the US central bank if her appointment is confirmed by the Senate.

Yellen, currently a Fed vice chairperson, emerged as favourite for the post after another possible pick, former Treasury secretary Lawrence Summers, pulled out of the running due to opposition from both Democrats and Republicans in the Senate.

She has spent more than a dozen years altogether at the Fed in various positions, including the last four years as vice chair.

If confirmed, Yellen would replace Ben Bernanke, who has been the chairman of the Fed since February 2006 and has overseen the US government's response to the US financial crisis.

Source: Agencies