The Supreme Court concluded two days of intense debate on gay marriage after suggesting it could strike down the law that prevents legally married gay couples from receiving a range of federal benefits that go to married people.

The court wrapped up its arguments Wednesday over the federal Defense of Marriage Act that bans recognition of same-sex marriages in the US, affecting several benefits available to married couples, including survivor benefits and tax breaks.

Justice Samuel Alito appeared to advocate a cautious approach to the issue on Tuesday, describing gay marriage as newer than such rapidly changing technological advances as cellphones and the Internet.

"You want us to assess the effect of same-sex marriage,'' Alito said. "It may turn out to be a good thing. It may turn out to be not a good thing."

US Supreme Court hears same-sex marriage cases

Justice Anthony Kennedy, the potentially decisive vote on a closely divided court, suggested that the court could dismiss the case with no ruling at all.

Kennedy said he feared the court would go into "uncharted waters" if it embraced arguments advanced by gay marriage supporters.

But lawyer Theodore Olson, representing two same-sex couples, said that the court similarly ventured into the unknown in 1967 when it struck down bans on interracial marriage in 16 states.

There was no majority apparent for any particular outcome and many doubts expressed about the arguments advanced by lawyers for the opponents of gay marriage in California, by the supporters and by the Obama administration, which is in favor of same-sex marriage rights.

On Wednesday, the court will hear the first challenge it has accepted to the 1996 federal Defense of Marriage Act, which defined marriage as a union between a man and a woman.

Recent polls suggest a rapidly growing number of Americans support allowing same-sex couples to marry, but there is no guarantee the conservative-leaning court rule in a similar direction.

Same-sex marriage is legal in nine states and in the District of Columbia but banned or limited in 41 others.

Rulings are unlikely before late June.