MINNEAPOLIS — One of the Twin Cities’ biggest health care mergers in two decades is on the horizon.

HealthPartners and Park Nicollet have signed an agreement to join operations. If federal and state regulators approve, the merged companies would create the state’s second-largest hospital system by revenue, behind Mayo Clinic in Rochester.

The hospitals and clinics involved will keep the names of their health care systems. The merger expands HealthPartners’ network of physicians and adds an array of specialty clinics. For the smaller Park Nicollet, it provides a more prominent market position against Allina and Fairview.

The Star Tribune (http://tinyurl.com/9huhxxg ) says the merged system will also be linked to HealthPartners’ insurance plan, which covers 1.4 million people, primarily in Minnesota and western Wisconsin.