Democrat Barack Obama complained on Wednesday that rivals Hillary Rodham Clinton and John Edwards have promised to mandate health care coverage without providing specifics on enforcement or affordability.

The presidential candidate fielded questions on a New Hampshire public radio call-in program and discussed his improved standings in state polls in Iowa and New Hampshire.

"When Senator Clinton or Senator Edwards say they're going mandate health care, but they haven't talked about either how to enforce it, or how to make it affordable to people, then it's not really a mandate. Anymore than if we mandate that people get car insurance. But (if) they can't afford it, they just don't get it," Obama said.

He said his plan correctly focuses on making health coverage affordable.

Addressing the problem of 47 million uninsured, Clinton has proposed a plan that would require every American to purchase insurance, either through their jobs or through a program modeled on Medicare or the federal employee health plan. Businesses would be required to offer insurance or contribute to a pool that would expand coverage. Individuals and small businesses would be offered tax credits to make insurance more affordable.

Clinton spokeswoman Kathleen Strand said the difference between Clinton and Obama is fundamental.

"Senator Clinton's health care plan covers every single American. Senator Obama's does not. Any health care plan that leaves 15 million Americans uninsured cannot be considered universal," she said.

Central to Edwards' plan is a so-called "individual mandate," requiring everyone to have health insurance the way most states require drivers to have auto insurance. Employers would have to insure their workers or pay into a government program that would provide coverage.

Obama's plan retains the employer-based insurance system and creates a public plan to expand coverage. But his plan does not include an individual mandate, leading critics to say it falls short of offering truly universal coverage.

The Illinois senator has defended the plan, arguing that until the cost of coverage is vastly reduced, many consumers wouldn't be able to buy insurance even if they were required to do so.

Obama, a first-term Illinois senator, also responded again to Clinton's recent argument that the country can't afford to give on-the-job training to its next president.

"These criticisms generally come from people who have been in Washington for a very long time and haven't done anything on the issues that are precisely the concern of the American people," Obama said, citing health care and energy.

A recent poll in New Hampshire showed Obama still trailing Clinton, but he had cut her lead nine percentage points since September. A survey in Iowa showed Obama up by a few percentage points, within the poll's margin of error.

"We just campaigned more in Iowa and we just started running television ads in New Hampshire a couple of weeks ago, so people are still getting a sense of who I am here in New Hampshire, what I stand for," Obama said.

"We are not entirely surprised that some of that hard work is starting to pay off."