WASHINGTON (AP) — The Biden administration has sued to block the merger of two of the world's largest insurance brokers, asserting the deal could eliminate competition, raise prices and hamper innovation for U.S. businesses, employers and unions that use the companies' services.

The Justice Department on Wednesday announced the antitrust suit filed in federal court in Washington seeking to stop AONs proposed $30 billion acquisition of rival benefits and risk consultant Willis Towers Watson.

Justice Department officials said the proposed merger would bring together two of the "Big Three" global insurance brokers — the third is Marsh McLennan — and eliminate competition in five markets. They are property, casualty and financial risk, health benefits, actuarial services for certain pension plans, retiree insurance exchanges and reinsurance.

The companies provide guidance to many major U.S. companies on administering health and retirement benefits, with the aim of keeping costs down by managing risk.

From the tone of their joint statement Wednesday, the companies appeared inclined to contest the government's case. They said the Justice Department's action "reflects a lack of understanding of our business, the clients we serve and the marketplaces in which we operate."

The two companies said that the combination "will accelerate innovation on behalf of clients creating more choice in an already dynamic and competitive marketplace."

In seeking separate approval for the merger from European Union authorities, the two companies agreed to divest some of their assets. But Justice Department officials said Wednesday those would not be sufficient to protect U.S. consumers.

Both companies are based in London and incorporated in Ireland. AON, with about $11 billion in revenue last year, has some 100 offices in the U.S. Willis Towers Watson, with around $9 billion in 2020 revenue, has 80 U.S. offices.

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This story has been corrected to provide the correct spelling of Marsh McLennan.