California's Supreme Court gave the final green light today for gay marriages to begin later this month, rejecting requests for a delay in introducing the measure.
The US state's highest court had ruled last month that refusing homosexuals the right to wed violated the state constitution.
Opponents quickly asked the court to halt the start of gay weddings pending a ballot measure to be put during the November elections that would limit marriage in California to a union between a man and a woman.
"It would have been unprecedented to postpone constitutional rights based on speculation of how a political scenario may or may not play out," San Francisco city attorney Dennis Herrera told Reuters.
"Folks can get married on June 17," he said.
The court was divided 4-3 in denying a petition to stay the decision. The same judges voted the same way on May 15 in the landmark decision, which was hailed by gay activists and condemned by social conservatives.
The court said its original ruling would become final at 5 pm on June 16, opening the way for gay marriages to start the next day.
Massachusetts is the only US state that allows same-sex marriage, but offers marriage licenses only to state residents. California has no residency requirement, which means gay people from across the United States could go to San Francisco and other cities to marry.