In the mind-boggling array of approaches to reforming America's crushingly inefficient health care system, the central questions are: How can we make health insurance affordable for more people? And how can we pay for it?

But the most divisive element has been government's proper role in driving down costs through an increase in choice and competition.

This week President Obama — who for too long has struck an aloof pose by advocating only for vague reform goals — promised to sharpen his pencil and push for an overhaul, outlining more specifically what he wants. That exposition is due Wednesday in the form of a major address on what aides call a "new phase" in the health care debate.

That's good. But so far the cloudiest part of his position remains murky. Obama has yet to unscramble what have been mixed signals over the controversial "public option" — a government-sponsored insurance plan to compete with privately sold coverage.

So far, the public option is still the most sure-fire way to compel competition in a marketplace that, in most localities, remains a near-monopoly, with very few players setting the price of health care coverage. The drawback — and in a recessionary age, it's a big one — is finding the fairest way to finance the added cost to the federal government.

Obama insists that he is open to other strategies to enable the same end goal of an increasingly consumer-friendly health insurance marketplace. But just opening the door doesn't make it happen. The administration has to seek out such workable alternatives and identify them to the public, if it seeks a compromise position.

Up to this point, the alternatives have been problematic. Many Republicans favor a private-sector solution that would enable consumers to cross state lines and buy insurance nationwide. Health care is a commodity, they say, and its prices will respond to market forces.

But shopping for health insurance isn't the same as scouring the ads or the Internet for a new car. If there is a single refrain to be extracted from the noisy protests at town-hall forums last month it is this: Americans are leery of change. That's why Obama has been so insistent in his assurance that people who like their insurance will be able to keep it.

The complexities of insurance plans are intimidating, so there's less of a drive to bargain-hunt, sapping the power of a free-market solution, by itself, to drive down prices. One illustration: The Kaiser Family Foundation has studied Medicare Part D, the Bush administration's prescription drug entitlement that also sought to expand choice. It found that while premiums rose for the more popular plans, only 6 percent of enrollees voluntarily left to search for a better deal.

Private co-ops also have been suggested as an alternative to government insurance. Although there are models of very competitive and successful co-ops — the Seattle-based Group Health among those cited the most — they can't be quickly or cheaply replicated from coast to coast.

It may be that an incremental approach toward the public option is needed. Senate Republican Olympia Snowe has proposed a trigger to authorize the public option should private companies fail to lower costs on their own by a set deadline. That merits some consideration; or there may be another way to phase in basic coverage in a public plan, with an emphasis on preventive care, expanding it as efficiencies and savings are achieved.

Prospects for a government plan also might brighten if Obama can lay out credible strategies for financing the estimated $900 billion cumulative cost over 10 years. Where would the projected $500 billion in Medicare cuts be found?

And who should bear the burden of additional taxes that surely would be needed as well? One Senate proposal, that would tax the health coverage benefit that many employees receive as part of their income, seems fairer than simply adding an assessment on the upper-income earners, as the House suggests. In this economy, neither plan is ideal.

The president has made the case that Americans can't afford a health care system that takes a larger bite out of diminishing pay packets every year.

But Obama now needs to be less of a cheerleader and more of a player. He must head to the field with a game plan that points out the mechanisms for effecting more affordable coverage. Simply identifying the goals is not a winning strategy.