NEW YORK — Walmart will now allow workers’ same-sex partners to participate in its company health benefits, bringing policies at the largest private employer in the United States in line with most of the nation’s top businesses.

Full-time associates’ spouses and domestic partners will be eligible for coverage in medical, dental, vision, life, critical illness and accident plans, the Bentonville, Ark.-based company said in a postcard to employees this week that was provided to Bloomberg.

Walmart, a frequent target of labor-rights groups pushing for better pay and benefits, said it made the change to have a consistent policy for all 50 states as some alter their definitions of marriage. Among Fortune 500 companies, 62 percent offer health-care benefits to same-sex partners, up from 34 percent in 2002, according to the Human Rights Campaign.

“Walmart, as America’s largest employer, has sent a cultural signal that equality for LGBT people is the simplest of mainstream values and we look forward to continuing to work with them,” Chad Griffin, president of the Washington-based group, said Tuesday in an emailed statement, referring to lesbian, gay, bisexual and transgender people. Griffin said he worked at Walmart as a teenager and was “moved” by the decision.

Walmart has 1.3 million full- and part-time U.S. employees, he said. More than half participate in health-care plans. A total of 1.1 million employees and family members are covered by the plans, he said.

The retailer’s definition of domestic partners includes same- or opposite-sex spouses, unmarried partners who live together for at least 12 months, aren’t married to anyone else and plan to continue sharing a household indefinitely, Hargrove said.

“We thought it was important to develop a single definition for all Walmart associates in the U.S. to give them consistency in the various markets we operate in across the country,” Randy Hargrove, a Walmart spokesman, said in telephone interview.

Walmart fell 0.2 percent to $72.86 at the close in New York. Thirteen states and the District of Columbia allow gay marriage.