HARRISBURG — Highmark executives and allies dominated a hearing before the state’s top insurance regulator Monday, seeking a green light for the insurer to transfer $175 million into its Western Pennsylvania hospital network to help it compete against rival University of Pittsburgh Medical Center.

At the four-hour session, state lawmakers, local elected leaders and a health care workers’ union were among those urging acting Insurance Commissioner Teresa Miller to approve the plan to tap Highmark’s $5.5 billion insurance reserve and use the money for grants to the eight-hospital Allegheny Health Network.

Planned capital improvements include modernizing Highmark’s two flagship hospitals in Pittsburgh, building outpatient service centers in areas where Highmark customers lack in-network options and expanding access to emergency and trauma services in some areas.

Residents of the region “need a viable competitor to the UPMC health system,” said state Sen. Randy Vulakovich, R-Allegheny, asserting complaints about UPMC are “the No. 1 thing that comes up” when constituents call him.

Said Rich Fitzgerald, the elected Allegheny County executive, “Obviously we should do everything we can to encourage the two systems to share this space.”

The executives stressed that Highmark Health — comprising Highmark, which administers the health insurance plan, and the Allegheny Health Network, which oversees the hospitals — is financially solid and well diversified.

Karen Hanlon, executive vice president and chief financial officer, said Highmark Health’s total revenues grew by $1 billion to $16.8 billion last year, but was vague when Miller and her staff pressed for details about the longer-term cost of capital improvements.