Obama urges court to overturn gay marriage ban
The Obama administration has filed a last-minute "friend of court" brief to the US supreme court, in support of a legal challenge to California's Proposition 8, which states that marriage can only be between a man and a woman.
The case is due to be held on 26 March and will seek to determine whether the 2008 law is unlawful under the United States constitution.
Solicitor General Donald Verrilli says in the brief that US states cannot give all the benefits of marriage to LGBT couples, without calling it marriage.
If approved, the decision would also affect seven states which allow civil partnerships between same-sex couples, according them almost all the rights as a married heterosexual couple, but do not define such unions as a "marriage".
Support for the brief has come from several high profile companies such as Apple, Facebook, Google and Nike, as well from a broad coalition of political parties and interest groups.
At a press conference, Jim Kolbe, a former Republic Congressman, said: "I'm proud to join more than one hundred other Republicans who believe gay Americans shouldn't be excluded from the fundamental right to marry the person you love.
"As a Republican I believe in protecting individual freedoms and that everyone — including gay and lesbian Americans — has a constitutional right to be treated equally under the law."
Labour unions also joined in the call for marriage equality.
Valarie Long, the executive vice-president of the Service Employees' International Union, said: "Working people are standing alongside millions of other Americans in this fight for marriage equality because we believe in fairness and equality and don't think federal or state law should penalise people simply because of who they love."