President Barack Obama's health care overhaul is on track in many states, the White House asserted Wednesday. But officials said the administration is preparing a federal backstop anyway for states in which opposition to the new law has blocked planning.

The law calls for states to build new health insurance markets called exchanges, so that millions of middle-class people who are currently uninsured can buy taxpayer-subsidized private coverage.

It also expands eligibility for Medicaid so low-income adults who have no dependent children can get government insurance. Putting the two approaches together, more than 30 million Americans are expected to gain coverage starting in 2014.

But 26 states are asking the Supreme Court to overturn the health care law, and many of those have made little progress in planning their exchanges, even though the deadline clock is ticking. The law says state plans must be approved by January 1, 2013 -- a year in advance of the program's launch -- or the federal government will step in and run things.

"No matter where you live, on January 1, 2014, an exchange will be up and running," deputy chief of staff Nancy-Ann DeParle said on the White House blog.

An accompanying progress report said 28 states and Washington, D.C., are "on their way" toward establish exchanges, widely considered the operational linchpin of the health care law.

With a presidential election and Supreme Court decision on the fate the health care law coming first this year, 2014 seems like a long way off even if Obama's signature domestic accomplishment is upheld. But to federal and state officials planning for exchanges, time is short. A totally new marketplace must be created, along with systems for verifying and safeguarding confidential personal information used to determine eligibility.

The White House report put a rosy outlook on the progress in some states.

For example, the report highlighted Idaho among states advancing. Republican Gov. Butch Otter strongly supports a state-run exchange, and his administration has received a $20-million federal grant to start work. But the legislature has to approve the actual spending of the money, and Republican foes of the federal health care overhaul are trying to block Otter from moving ahead. The issue is one of the most highly contested in this year's legislative session.

(Copyright 2012 by The Associated Press. All Rights Reserved.)

More From New Jersey 101.5 FM