Exxon Mobil Corp. said Friday that it will begin offering benefits to legally married same-sex couples in the U.S. for the first time starting next week.

The company says it will recognize "all legal marriages" when it determines eligibility for health care plans for the company's 77,000 employees and retirees in the U.S.

That means if a gay employee has been married in a state or country where gay marriage is legal, his or her spouse will be eligible for benefits with Exxon in the U.S. as of Oct. 1.

Exxon, which is facing a same-sex discrimination complaint in Illinois, said it was following the lead of the U.S. government. In June, the U.S. Supreme Court struck down the Defense of Marriage Act, which had allowed states to refuse to recognize same-sex marriages granted in other states. In recent months, federal agencies have begun to offer benefits to legally-married same sex couples.

"We haven't changed our eligibility criteria. It has always been to follow the federal definition and it will continue to follow the federal definition," said Exxon spokesman Alan Jeffers in an interview.

Jeffers said the company offers benefits to same-sex couples in 30 countries, consistent with local laws.

But Exxon has been criticized for declining to offer same-sex benefits or explicitly ban discrimination against gay and transgender workers at a time when many other big companies, including rival oil companies, have done so.

In a ranking this year of corporate anti-discrimination policies to protect gay, lesbian and transgender workers by the Human Rights Campaign, a national gay-rights group, Exxon ranked last.

The company is facing a complaint in Illinois for allegedly discriminating against a gay job applicant. Exxon says the complaint is without merit.

Tico Almeida, founder and president of Freedom to Work, a gay-rights group involved in the Illinois case, commended Exxon for changing its benefit policy, but criticized the company for "dragging its feet."

"It's a shame Exxon waited until after the Labor Department issued official guidance explaining that their old policy does not comply with American law," Almeida said.

Jonathan Fahey can be reached at http://twitter.com/JonathanFahey .