Steward Health Care System and Mercy Health System of Portland, Maine, have terminated a letter of intent signed last August under which Boston-based Steward would have bought the financially struggling Catholic hospital group in its first out-of-state acquisition.

In a terse statement issued late Friday afternoon, Steward said it had “entered into a period of exclusive negotiations but (was) unable to come to a definitive agreement” with Mercy Health. “As a result,” Steward said, “the letter of intent is terminated.”