U.S. health insurer Anthem Inc. said it's raising its offer to buy smaller rival Cigna Corp. for about $47 billion, including cash and stock. Indianapolis-based Anthem said Saturday it's proposing $184 per share, about 31 percent of that would be in Anthem shares and the remainder in cash. The offer represents a premium to Cigna's stockholders of 18 percent over Cigna's closing stock price on Friday. It said the bid also represents a premium of 35.4 percent based on the closing price of Cigna's shares on May 28 when reports of industry merger talks began. Anthem said the total transaction is valued at nearly $54 billion, including debt.The announcement comes as investors have been speculating for weeks about the possibility of a major acquisition in a sector where size is becoming increasingly critical. Health insurers also have been hoarding cash from recent strong quarters and doing little to tamp down merger talks. Last month, there were reports that another rival, Humana, ınc., was exploring a sale of itself.Some analysts predict that the nation's five biggest health insurance carriers, which also include Aetna and UnitedHealth Group, will eventually consolidate into three.Anthem said it has been in talks with Cigna, based in Bloomfield, Connecticut, to explore a potential combination since August 2014 and said it made its proposal public because the companies have not been able to come to an agreement. The company also said it has submitted four written proposals since early June, and made previous offers of $174 per share and $178 per share, according to a letter written by Anthem's CEO Joseph Swedish to Cigna's board of directors that it made public Saturday. But Anthem said that a big sticking point has been what role David Cordani, CEO of Cigna, is seeking to have at the combined companies. In the statement, Anthem said that the combined company would be "an industry leader" with greater than $115 billion in annual revenue. It noted Anthem and Cigna together "would gain meaningful diversification" covering about 53 million combined medical members and strong commercial, government, consumer and specialty franchises.Meanwhile, Cigna would bring its leadership position, broad geographic reach and national account presence as well as its expertise in many facets of the commercial market, Anthem said.The health care industry is facing intense pressure to squeeze out costs and find ways to capture opportunities arising from the Affordable Care Act.