Wal-Mart is to offer more employees low-cost health insurance after being fiercely criticised for not doing enough to support its staff.
More Wal-Mart staff now have health insurance
The world's largest retailer wants to expand its cheapest insurance scheme - in which staff pay $11 (£6) a month - to half its US workforce by next year.
It also plans to cut the length of time that part-time staff and their children must wait before they become eligible.
Separately, Wal-Mart is to open healthcare clinics in 50 of its stores.
Consultations at the walk-in clinics will cost about $50 per visit.
The clinics are designed to provide a cost-effective option for the millions of Americans who have no health insurance.
Many uninsured Americans use hospital emergency rooms where consultations, on average, cost more than $380.
Wal-Mart, America's largest private-sector employer, has been under growing pressure to improve its staff healthcare benefits amid concerns about the spiralling costs of state-funded medical programmes.
Proposals have been drafted in 20 states to compel Wal-Mart to spend more on employee healthcare benefits.
Maryland has passed legislation requiring the retailer to boost spending so or to reimburse the state-funded Medicaid scheme.
According to Wal-Mart figures, 615,000 staff out of its 1.3 million workforce were enrolled in company healthcare schemes in January.
The introduction of low-cost premiums ranging from $23 to $11 a month have persuaded an extra 70,000 staff to sign up for cover.
In a speech due to be delivered on Sunday, Wal-Mart chief executive Lee Scott will call for government and business to work more effectively together to tackle the increasingly prohibitive cost of healthcare.
However, according to extracts of the speech released by the retailer, Mr Scott will also say that business cannot provide a panacea for the 40 million Americans without health cover.
"The soaring cost of health care in America cannot be sustained over the long term by any business that offers health benefits to its employees," Mr Scott will tell a meeting of state governors.