A group of major city mayors are launching a push for gay marriage at the U.S. Conference of Mayors in Washington, D.C., Friday.

The mayors of Boston, Houston, Los Angeles, New York, and San Diego are co-chairing the group known as Mayors for Freedom to Marry.

More than 70 city leaders, including Chicago Mayor Rahm Emmanuel, are pledging to make the case for gay marriage in their communities.

"I'm going to support it because I think it's the right thing and it's consistent with our values," Emanuel said Thursday.

"To me, marriage is a recognition of love and the state should not be in the business of discriminating," he added.

The group will also be linked to the Freedom to Marry advocacy group which is campaigning to overturn the Federal Defense of Marriage Act or DOMA.

DOMA defines marriage in the U.S. as being between a man and a woman.