Eastern Maine Healthcare Systems said it signed a nonbinding letter of intent to acquire Mercy Hospital, a 168-bed hospital in Portland, Maine, which was previously in talks to be purchased by Steward Health Care System.

Eastern Maine Healthcare Systems, based in Brewer, is one of the largest systems in Maine and owns seven hospitals. Mercy Hospital is owned by Catholic Health East.

In a joint news release issued Friday, Eastern Maine Healthcare Systems and Mercy said they would begin seeking regulatory and canonical approval immediately. Spokeswomen for both organizations declined to provide additional information.

It's the second out-of-state deal this year to fall through for Steward, the Boston-based health system formed two years ago when Cerberus Capital Management acquired the six-hospital Caritas Christi Health Care system.

Steward, which now owns 10 hospitals in Massachusetts, backed out of a years-long effort to acquire Landmark Medical Center in Woonsocket, R.I., in September.

The proposed deal between Steward and Mercy was announced in August. At that time, Catholic Health East President and COE Judy Pershichilli said the system had explored “several alternatives” for Mercy prior to the announcement.

In an e-mailed statement, a Steward spokesman said Steward and Mercy had entered in “exclusive negotiations but were unable to come to a definitive agreement. As a result, the letter of intent is terminated.”

A merger between Catholic Health East and Trinity Health, two of the largest Catholic health systems in the U.S., is currently under way.