Congress faces a midnight deadline to reach an agreement or force federal agencies to close
Obama said on Monday he would talk to congressional leaders later about the US government shutdown,
During an Oval Office appearance with visiting Israeli Prime Minister Benjamin Netanyahu, Obama said he supported a Senate bill that would allow for a short-term funding of the government without cutting funding from his signature healthcare law, which Republicans are seeking to gut.
Obama said he planned to talk to congressional leaders later on Monday as well as on Tuesday and Wednesday.
"I am not at all resigned" to a shutdown, he said.
Obama said all involved must sit down in good faith without a threat of a debt default because the US dollar is the reserve currency of the world and "we don't mess with that."
Obamacare push accelerates
Meanwhile, the Obama administration accelerated its push to persuade individual Americans to sign up for the most extensive overhaul of the US healthcare system in 50 years, as the programme's foes in Congress fought to delay its launch with the threat of a federal government shutdown.
In opinion pieces featured in nearly 30 local newspapers, Vice President Joe Biden and Health and Human Services Secretary Kathleen Sebelius urged millions of uninsured Americans to ignore the battle in Congress over US President Barack Obama's healthcare law, and instead focus on the access their families need to medical services.
"Come Tuesday, Americans will be able to see for themselves that the Affordable Care Act isn't actually about Washington politics," Biden wrote in a piece printed in outlets including the Des Moines Register in Iowa and the Birmingham News in Alabama.
"It's about regular people shopping for insurance they can finally afford, and purchasing security and peace of mind along with it."
The key element of the president's healthcare reform, known widely as Obamacare, was due to launch on Tuesday with the opening of online insurance exchanges in all 50 states and the District of Columbia offering subsidised health coverage.
State officials and community groups on Monday said they were putting the final touches on their exchange openings.
Obamacare
The Department of Health and Human Services said that 900 businesses and organisations had volunteered to explain the new law to Americans nationwide.
The roll-out would proceed even as Republican lawmakers fought to delay the overhaul by attaching amendments to a government funding measure.
Congress faces a midnight deadline to reach an agreement or force federal agencies to close, or partially close, at the start of the US fiscal year on October 1.
Republican US Representative Charles Boustany of Louisiana, a leading Obamacare critic, expressed misgivings ranging from the cost of coverage to the role of the Internal Revenue Service, a favorite target for conservatives that will help determine eligibility status and subsidy levels for applicants.
"We know that the IRS is in the mix of this … We know there are major problems there. I have really deep concerns about where this is going," he said on Fox News.
As many as 7-million Americans are expected to sign up for health coverage via the new exchanges for 2014, the year Obamacare's main provisions take effect.
Another 8-million are expected to receive benefits through an expansion of the government's Medicaid program for the poor.
The Affordable Care Act, passed in 2010, requires that health insurance companies provide a basic package of benefits and prohibits them from excluding people due to prior illness.
It provides billions of dollars in government subsidies, in the form of tax credits, to help individuals buy insurance on the basis of annual income.
It also requires that all Americans obtain insurance, or pay a fine.
Republicans and other groups have fought the law for creating what they say is an intrusive government system to oversee healthcare that will place financial burdens on individuals and businesses.
Exchanges set to open for business
New York, Colorado, Oregon and some other states running their own exchanges plan to open at 8am (12pm GMT) on Tuesday, while others may open as early as midnight.
Senior administration officials say they would prefer to have people accessing the federally-run marketplace for 36 states during daylight hours when government and call center offices are fully staffed.
It promises to be a rocky roll-out. Several exchanges, including Oregon, Colorado and the District of Columbia, have already said key functions for enrolling won't be in place in the first few weeks of October.
Over the summer the Obama administration delayed numerous provisions of the law, most notably the requirement that large employers provide health insurance to their workers starting in 2014, as well as elements of the exchanges, such as their ability to sell policies to small employers and their workers and a Spanish version of the main website.
Software problems threaten opening-day glitches. Over the weekend, armies of information technology specialists tested and re-tested the complex interfaces and communication links needed to make the exchanges functional.
As opening day neared, many exchanges continued to ramp up education and marketing efforts. Kynect, Kentucky's exchange, handed out information at the Kentucky Bourbon Festival.
Minnesota's exchange, as well as HHS, held live online chats to get the word out.
Exchange functioning
From insurance companies to hospital executives to policy experts and politicians, there will be intense focus on how the exchanges function, and how many customers they attract, from the opening bell.
For weeks, however, the Obama administration as well as states have played down expectations for October 1.
"We are expecting a slight upturn of activity," Rebecca Lozano of the Portico Health Net, a Minnesota group that will help people enroll in coverage, said last week at an event hosted by Families USA, a non-profit that supports the ACA.
"We're not imagining a run on the banks" on October 1.
"Those with preexisting conditions are the people we expect to be at the door when the door opens," said Reagan Hunt, executive director of Kentucky Voices for Health.
"We have no idea what that number looks like. But in Kentucky, you have about 900 000 people who have been denied coverage in the past due to preexisting conditions."
Sebelius said on Monday that "the key date really is the 15th of December," the deadline for buying coverage that starts on January 1.
"For millions of Americans, the new options are going to be affordable, within their own budgets. So January 1 can be a new day. It can begin to change the statistics where we will no longer have a large population in this country who doesn't have access to the best medical care." – Reuters