The Supreme Court on Tuesday strengthened the power of the Federal Trade Commission to block hospital mergers, issuing an opinion that could limit the ability of public hospital authorities to claim immunity from federal antitrust laws.

The unanimous decision restored the authority of the F.T.C. to challenge the merger of the only two hospitals in Albany, Ga.

Some experts said the decision could mean that hospitals will have to be more cognizant of antitrust considerations when they join forces with other health care providers to form so-called accountable care organizations, as called for in the new health care law.