Insurer Aetna (AET) has signed a deal to buy rival Coventry Health Care (CVH) for $5.7 billion in cash and stock, the latest in a string of multi-billion-dollar acquisitions in the U.S. healthcare sector.

Aetna is paying $42.08 a share for Coventry, a 20.4% premium to Friday's closing price, The Wall Street Journzl said, citing people familiar with the matter.

If the deal goes through, it will be the latest example of companies focusing on increasing their government business to benefit from a favorable U.S. healthcare reform.

Earlier this year, the U.S. Supreme Court upheld President Barack Obama's healthcare law, which aims to extend coverage to more than 30 million uninsured Americans.

The U.S. healthcare reform, passed in 2010, aims to provide coverage for 16 million more Americans through privately run health insurance exchanges in each state, and will expand Medicaid eligibility for an additional 16 million people by raising limits on household income.

The acquisition of Coventry will help Aetna to lift its share of revenue from its government business to over 30 percent from 23 percent, the Journal reported.

Aetna and Coventry Health Care were not immediately available for comment.

In July, health insurer WellPoint said it would buy rival Amerigroup for $4.46 billion, nearly doubling its Medicaid business.

Last October, Cigna agreed to buy HealthSpring Inc for $3.8 billion to strengthen its Medicare business.

The boards of Aetna and Coventry have approved the deal, which is expected to be announced on Monday, the report said.

Aetna expects the acquisition to add about 45 cents per share to its 2014 earnings and expects to boost its 2015 earnings by 90 cents per share, the Journal said.

(Reporting by Bijoy Koyitty in Bangalore; Editing by Edwina Gibbs and David Holmes.)