MINNEAPOLIS (WCCO) -- Minnetonka-based UnitedHealth Group has reportedly approached rival Aetna with a possible merger deal.

The takeover deal is valued somewhere around $40 billion, according to a report in the Wall Street Journal.

The offer is just one of a series of mega-merger proposals around the insurance industry in the past few weeks.

Health insurers are under increased pressure to grow as a way to cut costs, as more of their business comes from government programs and health exchanges as traditional employer-based coverage dries up.

If UnitedHealth were to purchase Aetna, they would become the world's largest health care provider.