New York state is also considering a law to allow same-sex marriage
Lawmakers in New Hampshire have rejected a bill that would have granted marriage rights to gay couples.
The state's Senate passed the bill, but the House of Representatives voted it down by 188 votes to 186.
The chamber had approved an earlier version of the bill, but blocked the new version, which included legal protections for religious groups.
The state's governor, John Lynch, threatened to veto the bill if it did not include religious exemptions.
The issue is a controversial topic in the US, and many states have passed bills and constitutional amendments banning gay marriage.
Five US states - Massachusetts, Connecticut, Vermont, Iowa and Maine - now allow same-sex marriage, and legislation is being considered in New York state.
In New Hampshire, the bill will now go back to the state's Senate, where lawmakers will attempt to draw up a compromise.
In California, the state's Supreme Court is expected to rule shortly on whether last year's vote banning gay marriage in the state was constitutional.