Gay marriage advocates plan to visit Philadelphia's City Hall on Tuesday to seek marriage licenses or have their out-of-state marriages recognized.

Organizers Bob and Bill Sullivan of South Philadelphia say they married four years ago in Vermont, but don't enjoy the legal benefits of marriage in Pennsylvania.

Bill Sullivan has been unable to get a driver's license after taking his husband's name.

And he relies on public disability support because he's not covered under Bob's insurance.

Marriage Equality USA says the momentum "appears unstoppable" after federal court judges struck down same-sex marriage bans in Virginia, Utah and Oklahoma.

In Pennsylvania, a key test case is scheduled for trial in federal court in Harrisburg in June.

The Philadelphia event Tuesday is rescheduled from Valentine's Day, when a snowstorm closed City Hall.