Gay civil rights groups trying to build momentum for a possible Supreme Court showdown filed two lawsuits yesterday that seek to strike down portions of a 1996 law that denies married same-sex couples federal benefits.

The lawsuits were filed in federal courts in Connecticut and New York and come just months after a federal judge in Boston struck down a key component of the federal Defense of Marriage Act.

The legal actions seek judicial declarations that the law enacted by Congress in 1996, when it appeared Hawaii would soon legalize same-sex marriage, was unconstitutional because it prevents the federal government from affording pension and other benefits to same-sex couples.

Since 2004 five states — Connecticut, Iowa, New Hampshire, Vermont and Massachusetts — and the District of Columbia have legalized gay marriage.

In Hartford, Conn., the Gay & Lesbian Advocates & Defenders sued the federal government on behalf of a Connecticut widower and married couples from Connecticut, Vermont and New Hampshire.

The other suit was filed on behalf of a New York woman, Edith Schlain Windsor, who met her late spouse, Thea Clara Spyer, nearly a half-century ago at a restaurant.

"No one should have to fight with the government after losing the person she’s loved for more than four decades," said Donna Lieberman, executive director of the New York Civil Liberties Union. "Edie and Thea made the same lifelong commitment that other married couples make, and their marriage deserves the same dignity, respect and protection afforded other families."

Mary Bonauto, an attorney with Gay & Lesbian Advocates & Defenders, said the Connecticut lawsuit was filed to maintain the momentum the group gained with the success of its challenge against the law in Massachusetts.

The Justice Department said in a statement that it had no response to the lawsuits, except that the government "is defending the statute, as it traditionally does when acts of Congress are challenged."