PITTSBURGH — The Department of Justice says the state’s largest health insurer can buy the West Penn Allegheny Health System in Western Pennsylvania.

A department statement issued today says the proposed merger between Highmark and West Penn could bring increased competition to the regional health care market.

Highmark, based in Pittsburgh, signed a $475 million agreement last November with the six-hospital West Penn Allegheny system. But federal officials had to review the plan and certify that it didn’t break antitrust laws.

The deal will provide a financial cushion for West Penn Allegheny, which has lost money in recent years.