NEW YORK — Twenty of the country’s largest corporations, including American Express Co., Coca-Cola Co. and Macy’s Inc., have banded together to rein in employee health care costs.

The companies have formed Health Transformation Alliance (HTA) to break with wasteful and inefficient marketplace practices that have resulted in employees paying higher premiums, co-payments and deductibles every year.

“The current system is unsustainable, and it costs our employees too much,” said Kevin Cox, chief human resources officer (CHRO) at American Express. “Even the most successful companies won’t be able to afford the rising costs of health care in the not-too-distant ­future.”

“Our priority in this coalition is supporting positive health outcomes for our strongest asset — our employees,” said Caterpillar Inc. CHRO Kim Hauer. “Health care benefits are too important to our people for us to sit on the sidelines; the status quo needs to change, and we have to be part of the solution. We are creating a better way of getting workers what they want and need.”

The initiative will focus on reforms to the supply chain to reduce redundancies that drive up the cost of health care coverage. By coming together to share expertise, the companies are seeking to make the current multilayered supply chain more efficient.

Collectively, the 20 companies are responsible for health care benefits for 4 million people, spending more than $14 billion annually on health care for employees, their dependents and retirees. HTA will serve as part of each company’s health strategy, bringing increased innovation, better analyses of the latest data and greater leverage into how corporations obtain coverage for their workers.

The alliance will be built and organized throughout 2016, and as early as next year will launch a pilot project to help employees obtain more affordable prescription medications. Other major initiatives are planned for 2018 or later.

“The American health care delivery system is a patchwork of complicated, expensive and wasteful systems,” said Marc Reed, chief administrative officer of Verizon Communications Inc. “We’ve done what we can as individual companies. By joining together, we can do more. We need to stop applying bandages to the system and address what’s fundamentally wrong.”

Other members of HTA include American Water, BNSF Railway Co., Brunswick Corp., E.I. du Pont de Nemours & Co., HCA Inc., Hartford Financial Services Group Inc., IBM Corp., Ingersoll Rand, International Paper Co., Lincoln Financial Group, Marriott International Inc., NextEra Energy Inc., Pitney Bowes Inc., Shell Oil Co. and Weyerhaeuser Co.