NEW CASTLE — A merger between the Jameson Health System and UPMC will be official Sunday and will be celebrated at a news conference Monday at the hospital’s north campus.

The merger will create UPMC Jameson, a deal worth $80 million, according to a news release issued Friday afternoon by Jameson.

The hospital’s patient base is mainly in Lawrence and Mercer counties.

Jameson has said that financial struggles led to the partnership.

Previously, the Butler Health System and Heritage Valley Health System made a joint offer to merge with the Jameson Health System for an undisclosed amount. Jameson had considered that bid and others received in a rebid process as “insufficient.”

Under the first offer, UPMC would have assumed $40 million in long-term debt as part of the deal, as well as $15 million in outstanding pension obligations.

The attorney general’s office denied that merger, concerned that a Jameson-UPMC partnership would control too much of the in-patient health care market in Lawrence County. This is estimated at more than 70 percent of the region’s inpatient services and could result in less competition and higher costs to patients.

However, the deal moved forward in January when independent arbitrator and former Chief Judge Donald Ziegler ruled in favor of the merger. Ziegler required Jameson to negotiate with UPMC to address antitrust concerns.