Local medical behemoth Partners HealthCare said it is "exploring new partnerships" with organizations including insurer Harvard Pilgrim Health Care, signaling a possible merger.

"As the healthcare environment changes and insurers and providers increasingly share financial risk, traditional relationships are shifting," said Partners spokesperson Rich Copp. "Partners HealthCare is constantly exploring new partnerships and relationships with other providers and insurers with the goal of improving the delivery of health care to patients both locally and around the world. Harvard Pilgrim is certainly among those organizations.

Both of our organizations are taking the opportunity to explore ways that we can work together to improve the patient experience and quality of care while controlling medical trend and reducing costly administrative burden."

Partners owns Brigham and Women's Hospital and Massachusetts General Hospital, and is known to be the largest health care provider in Massachusetts. Wellesley-based Harvard Pilgrim has about 1.2 million members.

News of the closed-door talks comes as the proposed merger of Beth Israel Deaconess Medical Center and Lahey Health face criticism from health care advocates, warning it would drive up health care costs and leave poor residents without access to services.

Partners already is known for providing some of the most costly services in the state.

Harvard Pilgrim confirmed the recent conversations, calling them "exploratory" and "very preliminary."

"As two leading and innovative health care companies, Partners and Harvard Pilgrim have been engaged in exploratory conversations regarding whether each of our strong organizations could be even more successful working together," the statement said. "We are assessing a number of potential models for how this could best work. This could involve a range of options from new contractual arrangements to deeper clinical, operational and financial integration of our organizations."

Harvard Pilgrim added, "while we are very excited about these conversations, they are very preliminary and no final agreements have been reached."