The American Medical Association added pressure on U.S. states to steer toward the system that opens doors to all insurers who meet minimum standards as they build up their health insurance exchanges.

The influential doctors group on Tuesday put its weight behind the so-called “open marketplace” structure of a health insurance exchange, as opposed to a model called “active purchasers.”

In the latter, a state would act much like a large employer and vet bids from insurers who want to participate.

The creation of exchanges is a key plank of President Barack Obama’s health reform passed last year. They are envisioned as competitive marketplaces of insurance plans that would allow uninsured people and small businesses to band together and negotiate cheaper rates.

U.S. health regulators have given states quite a bit of flexibility in establishing the exchanges, which are due to be functional by 2014, including the model they want to follow.

Some 500 AMA delegates representing doctors from all states voted on a resolution in favor of open-market exchanges “with strong patient and physician protections in place, to increase competition and maximize patient choice of health plans.”

Many states are still in the early stages of sketching out exactly how the exchanges will be structured.

With much opposition to Obama’s health reform and a looming Supreme Court decision that could discard the law’s pillar individual mandate provision, many states have been reluctant to finalize any specific plans.

To encourage states’ participation, the U.S. health agency overseeing the roll-out of exchanges said on Tuesday it hired Oregon insurance commissioner Teresa Miller as senior adviser for state outreach.

Oregon has been on the forefront of exchange work since the reform became law, and Miller is likely to take over some of the responsibilities of the exchanges chief Joel Ario, who left in September.

The federal government will pick up the slack in the states that do not have an exchange by the deadline, but it also has yet to unveil what the federal model would look like.

The operating exchange in Massachusetts is an example of an “active purchaser” model where the state has the power to bargain with insurers and shut out insurance plans it deems as inefficient or low-quality.

Utah’s current exchange is an “open marketplace” that effectively allows as many insurers to participate as are willing, offering consumers a wide variety of products.

Insurers have spoken against the “active purchaser” structure, saying it would limit consumer choices. Consumer advocates have supported such a model, arguing it would offer people perhaps fewer, but vetted, or higher-quality, options.

In a report by one of its councils, the AMA expressed concern that an “active purchaser” model could lead to a highly concentrated insurance market that may restrict the doctors’ ability to negotiate with insurers and threaten free competition among plans based on price and quality.

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By Alina Selyukh

NEW ORLEANS