Massachusetts lawmakers have agreed on a state constitutional amendment that would ban gay marriage and legalise civil unions.
Supporters and opponents of gay marriage were at the state house
Lawmakers finally agreed on the proposed amendment as they debated the issue for the third time in two months.
If the proposal passes further legal hurdles, it will go to the voters in a referendum in autumn 2006.
In the meantime, gay marriages are set to take place from mid-May, after a landmark court ruling.
No US state allows gay marriage, but the Supreme Court in Massachusetts last November ruled that it was unconstitutional to bar same-sex couples from the benefits of civil marriage.
That ruling, reaffirmed in February, is what prompted state legislators to seek a constitutional amendment.
Hundreds of supporters and opponents of gay marriage were at the Massachusetts state house in Boston on Monday, waving placards and shouting their views.
Chants of "equal rights" competed with cries of "one man, one woman".
Gay activists say the proposed civil unions do not go far enough, as gay couples would not be granted federal benefits, such as the right to file joint tax returns or receive social security benefits if one partner dies.
The proposed amendment asks voters to simultaneously ban gay marriage and legalise civil unions - rather than taking those steps separately.
It still has to survive two votes in the state legislature before it can go to the voters in 2006.
If the vote is passed, gay couples who plan to marry in the state from 17 May fear they could be stripped of their court-ordered marriage rights within a few years.
The issue of gay marriage has became an election year issue, with President George W Bush declaring his backing for an amendment to the US constitution that would ban same-sex marriages.
Several local officials have challenged state laws by issuing marriage licenses to gay couples in California, New York and other states.
San Francisco started issuing marriage licenses in February, allowing more than 3,400 gay weddings before Californian's Supreme Court ordered a halt last month.
The court has yet to rule on the legality of the existing marriages.
In 2000, Vermont became the first US state to offer gay couples the right to join in civil unions.