One of the biggest health insurers in the country, Anthem, on Saturday announced an offer to acquire a rival, Cigna, for more than $47 billion in cash and stock.

The move is the latest step toward an expected consolidation among health insurance companies. Last month, Humana, another competitor, was said to be exploring a sale of itself.

Driving the push to get bigger has been the Obama administration’s health care overhaul, which has bolstered revenues. Yet, at the same time, profit margins have come under pressure in the face of greater pricing transparency and less generous funding of government plans.

By going public with its offer, Anthem is seeking to stir up Cigna’s shareholders and force the company back to the negotiating table. Anthem said it had been in talks with Cigna over a potential combination since August.