WASHINGTON - The Supreme Court appears skeptical that state officials have the power to require health insurers to turn over reams of data revealing how much they pay for medical claims.

During oral arguments Wednesday, most of the justices seemed to agree that efforts by Vermont and other states to collect and publicize the data conflict with federal law governing certain health plans.

Vermont is one of at least 18 states that gather health care claims data in an effort to keep down health costs, increase competition and improve quality.

The case involves Liberty Mutual Insurance Co., which operates a self-insured health plan for its workers and refused to turn over data.

An appeals court sided with the company, saying the plan is subject to federal law, which pre-empts state-law reporting requirements.