Almost three-fourth of Americans claim that the legalisation of same-sex marriage is inevitable.
With the US Supreme Court due to rule on the hot button issue in a matter of days, the Washington-based Pew Research Center surveyed 1,504 adults on the topic during the first five days of May.
Seventy-two percent agreed when asked if legal recognition of same-sex marriage was "inevitable" -- including 59 percent of those who said they opposed allowing gays to marry legally.
Eighty-seven percent of respondents personally knew someone who is gay or lesbian -- and predictably, support for the legalization of same-sex marriage was strongest within that group.
"Yet opposition to gay marriage remains substantial," Pew's pollsters said, with 45 percent of Americans regarding homosexual behavior as a sin -- down from 55 percent in 2003 but on a par with those who don't see it as such.
Nineteen percent said they would be "very upset" if their child revealed being gay or lesbian.
Pew conducted its survey shortly before Rhode Island, Delaware and Minnesota became the latest of the 12 US states plus the District of Columbia to legalize same-sex marriage.
The constitutions in 31 of the 50 US states, as well as the federal Defense of Marriage Act (DOMA), still define marriage strictly as a union between a man and a woman.
The Supreme Court is expected to rule on the constitutionality of DOMA, and on a California voter initiative in 2008 that threw out that state's same-sex marriage law, sometime this month.
Pew posted its findings on its website: www.pewcenter.org