Aetna offered $230 (208 euros) per share, at a total of $34 billion, the two companies declared in a joint statement on Friday, though the deal is still subject to approval from shareholders and cartel authorities.

Aetna is hoping the acquisition will bring it millions more customers and a better position in negotiations with hospitals and doctors.

The deal between the two insurers is the conclusion of a protracted bidding war among all the biggest health care providers on the US market. Analysts and investors have been predicting a wave of mergers after the Supreme Court declared the Affordable Care Act - also known as Obamacare - as legal on June 25.

That decision was widely seen as the most conclusive of a string of legal challenges to the act.

The law, which was originally passed in 2010, has led to an increase in the number of those with health insurance in the US, plus more pressure on prices. As a result, some fusions have already taken place.

Mega-mergers

On Thursday, St. Louis-based health care provider Centene announced a $6.3-billion bid for fellow insurer Health Net to create a combined company with about 6 million Medicaid members, making it one of the largest in the country.

Medicaid is the state- and federally-funded program for the poor and people with disabilities, which the Affordable Care Act significantly expanded.

On June 20, Anthem went public with a more than $47 billion cash-and-stock bid for Cigna, which Cigna rejected in a letter sent to Anthem the next day.

"The wave of consolidation sweeping the (managed care) industry is accelerating as players seek to establish their own market position," Leerink analyst Ana Gupte said in a note to investors announcing the Centene deal.

Like other health insurers, the share prices of both companies have hit all-time highs this year and advanced much further than the broader market.

bk/pad (AP, dpa, Reuters)