Health insurer Anthem has publicly proposed acquiring competitor Cigna Corp. for $184 per share in a deal valued at $53.8 billion.Anthem’s play to take over Cigna marks the official first step in what observers saw as inevitable consolidation in the health insurance industry. But the transaction is far from a done deal because regulatory approvals and a battle over the CEO chair remain significant hurdles.Anthem’s deal is nonbinding and needs approval from Cigna’s board of directors and shareholders. The two insurers have been in negotiations since August 2014, and this represents the fourth offer since then. Anthem hopes to complete a deal by the end of the month.

Under the latest proposal, Anthem would pay $184 per share in cash and stock, or about $47.4 billion. Cash would represent 68.6% of the deal, and Anthem’s shares would make up the rest. Including debt, the deal would be worth $53.8 billion, Anthem said. Cigna shares closed Friday at $155.30.

“This combination is the absolute best strategy for both organizations to maximize the potential and lead the transformation of the healthcare industry,” Anthem CEO Joseph Swedish said in a statement.

However, Cigna CEO David Cordani has demanded he become CEO of the newly merged company. Anthem has offered for Swedish to stay in his CEO role and make Cordani president and chief operating officer, which Cordani has rebuffed. Swedish hinted that he would step down from his CEO role after two years after the merger, but there would be no guarantee Cordani would take over.

“We were stunned that the Cigna board continues to insist on a guaranteed CEO position for Mr. Cordani over choosing to allow its stockholders to realize the significant premium being offered,” Swedish wrote in a letter dated Saturday. “We therefore are now reaffirming our June 18 proposal for a combination of our companies, which we believe your stockholders will find more compelling.”

Further, Anthem would have to get antitrust approval from the Justice Department and licensure approval from the Blue Cross and Blue Shield Association. Anthem said it was “confident” it would get the OK from the Blues.

If Anthem and Cigna combined, the new company would have expected revenue of $115 billion this year, still a little smaller than UnitedHealth Group. But the giant would also have 53 million covered members, far surpassing UnitedHealth, and would be a leader in the fully insured and self-insured employer markets.

Anthem hired investment bank UBS as its financial adviser.