UnitedHealth Group Inc (UNH.N) said on Tuesday it agreed to buy MedSynergies, which manages physician practices, adding about 9,300 doctors to the hospital and health system services that its Optum technology-based business currently serves.

Financial terms were not disclosed.

UnitedHealth, the nation's largest health insurer, has been expanding beyond its core business of managing care for large employers and the government's Medicare and Medicaid programs through its fast-growing Optum business.

Optum clients include about 4,000 hospitals such as the Kaiser Permanante and Dignity Health systems. With the acquisition it will expand its reach to manage doctors and other healthcare professionals who are part of the 4,000 systems as well as add new systems like the Catholic Health Initiatives and Texas Health Resources.

Optum executive Bill Miller described the acquisition as substantial and said the move will offer a better view into patient care from when they first see a doctor to when they are discharged from a hospital.

Doctors, hospitals and payers such as insurance companies, employers and the government are trying to find ways to improve care while managing costs as the nation undergoes massive healthcare reform.