A New York hospital will provide spousal benefits to partners of its gay and lesbian employees, becoming the largest private employer in the United States to do so.

Montefiore Medical Center, which has about 9,000 employees, said Tuesday that gay couples would be eligible for such coverage as long as they prove that their living arrangements are similar to those of heterosexual married couples.Among other things, they would have to make sworn statements that they were each other's "sole domestic partner."

Montefiore, based in the Bronx, is the largest private business in the nation to recognize gay relationships, according to the American Civil Liberties Union.

It is "the most significant step for the domestic partnership movement to date. It also marks an important step forward for the equal rights of lesbians and gay men," said William B. Rubenstein, director of the ACLU's Lesbian and Gay Rights Proj-ect.

The change is also significant because the trend among cost-conscious private businesses is away from paying benefits for spouses.

"Montefiore has a long history of equal and fair treatment of all employees. We see this policy as a part of our commitment to the principles of fairness and equity," said hospital spokeswoman Barbara Janes.

Janes said the new rule would apply only to couples "who are unable, by law, to marry because of laws prohibiting marriage of persons of the same sex."

She and Rubenstein said they did not know how many employees would be eligible.