UnitedHealth Group is offering $236 million to acquire a large medical group in Massachusetts in a deal that would further expand the Minnetonka-based company's fast-growing clinic business.

The acquisition still requires final court approval, but it was cleared this month by the Attorney General's Office in Massachusetts.

Atrius Health is the largest physician-led nonprofit medical group in Massachusetts, with 1,000 employed clinicians and 30 practice sites, according to a state review last year.

"We are excited to be coming together to expand upon the exceptional health care services Atrius Health provides to Massachusetts," UnitedHealth Group said Friday in a statement.

The medical group would become part of the company's Optum division for health care services. Within that division, a unit called Optum Care provides health care and management services; it includes 53,000 physicians at 1,450 sites, the Massachusetts Health Policy Commission said in a review of the proposed deal.

Clearance by the attorney general was an "important milestone" toward completing the transaction, said Dr. Steve Strongwater, the president and chief executive of Atrius Health, in a statement.

"Combining with Optum will enable us to advance our ability to keep people healthy through enhanced services that improve the care experience and lower costs," Strongwater said. "As part of Optum, Atrius Health will remain committed to our same mission, vision, and values for patient care, and will continue to care for patients through multiple insurance plans."

Because Atrius Health is a charitable nonprofit, proceeds from the sale would transfer to a foundation that promotes patient health through programs, including education and training.

The medical group serves more than 690,000 adult and pediatric patients, but has been faced with financial challenges to continuing operations, according to an April 14 court filing by the state attorney general. The board of directors at Atrius reasonably concluded "the only option for preserving the value of Atrius' charitable assets and continuing its clinical operations would involve a sale of its assets to the for-profit Optum Care," the filing states.

In 2018, Optum Care acquired the nonclinical assets of Reliant Medical Group, another large clinic operator in Massachusetts. The unit has medical practices and networks in 16 states overall.

Beyond clinics, Optum operates urgent care and surgery centers and is pushing into other areas of outpatient medicine. In March, the company announced a $6 billion deal to acquire a Louisiana-based home-care company.