San Francisco Mayor Gavin Newsom put California right in the middle of the fight over same-sex marriage Tuesday, saying he wants the city to try to find a way to issue marriage licenses to gay and lesbian couples in defiance of state law.

Newsom's plan would make San Francisco the first city in the state to allow gays and lesbians to marry and would almost certainly lead to legal challenges. That in turn would force the California courts -- as state courts have in Hawaii, Vermont, New Jersey and Massachusetts -- to determine whether barring same-sex couples from marrying is discriminatory and unconstitutional.