A Washington Post / ABC News survey has revealed 58 per cent of Americans now back the legalisation of same-sex marriage with only 34 per cent opposed.
The results are an almost mirror image of a similar survey conducted in 2004, which showed 55 per cent of Americans were against same sex marriage with 41 per cent in favour.
The news comes at a tipping point for the gay marriage debate in the US with states once solidly in the anti camp, such as Texas, now on the verge of allowing same-sex unions.
Currently, 17 states plus the District of Columbia allow same-sex marriage with a further 10 allowing civil partnerships but stopping short of marriage. The findings put further pressure on the 33 states that explicitly ban same-sex unions.
A ruling in December by the US Supreme Court said restricting the definition of marriage to heterosexual couples was unconstitutional. Following the ruling, courts in Texas, Oklahoma, Utah and Virginia struck anti same-sex marriage laws from the statute books, pending appeal.
On major social issues facing LGBTI couples, 61 per cent of Americans are in favour of gay and lesbian couples being allowed to adopt and 81 per cent say businesses should not be allowed to discriminate against gay and lesbian customers.
However, schisms of opinion still remain. For instance, while 70 per cent of Democrat voters are in favour of legalising same sex unions, a majority (54 per cent) of Republican voters are against any such move.
Closer to home, a Fairfax Nielsen poll conducted in August 2013 found 65 per cent of Australians were in favour of same sex unions with only 28 per cent against.