UnitedHealth Group Inc . has joined the entreat for a section of Envision Healthcare Corp ., the health-services provider under pressure from activist investor Starboard Value, according to people familiar with the matter.

Envision has attracted affair from state insurer UnitedHealth for its ambulatory business component, said the people, who requested not to be identified as the details aren’t public. Separate an organization of private equity firms, including a consortium comprised of Hellman& Friedman, Onex Corp. and Clayton Dubilier& Rice, as well as one led by Carlyle Group LP, are still interested in buying the whole corporation but would also be open to acquiring percentages, the people said. A transaction could be announced in the next week, they said.