Brad Pitt has agreed to donate $100,000 to help the Human Rights Campaign raise money for its efforts to support same-sex marriage initiatives in several states, AP is reporting.

The nation's largest gay rights group said that Pitt agreed to match contributions from members up to $100,000.

It was a rare political donation for Pitt. In an e-mail to members of the Human Rights Campaign, Pitt wrote that it's ''unbelievable'' that people's relationships will be put to a vote on Election Day.

Same-sex marriage will be on the ballot in Maryland, Maine, Minnesota and Washington state.

Pitt and his girlfriend, Angelina Jolie, have said before that they wouldn't marry until gays were allowed to do the same, though they later went back on that when Pitt proposed to Jolie.