Hollywood star Brad Pitt is pledging $100,000 to the fight for same-sex marriage in four states where its future is on the ballot on Tuesday, the Human Rights Campaign said Wednesday.

In a statement, the HRC said the "Fight Club" and "Moneyball" star -- a vocal supporter of marriage equality -- was matching contributions from others in the run-up to votes in Maine, Maryland, Minnesota and Washington state.

"It's unbelievable to me that people's lives and relationships are literally being voted on in a matter of days," said Pitt in an email to members of the group, the nation's biggest gay rights organization.

"If you're like me, you don't want to have to ask yourself on the day after the election, what else could I have done?"

Same-sex marriage is not federally recognized, but it is legal in Connecticut, Iowa, Massachusetts, New Hampshire, New York, Vermont and the District of Columbia. It is constitutionally banned in 31 states.

Pitt is engaged to actress and longtime partner Angelina Jolie, but he has often stated that they will not wed in the United States so long as marriage equality is not the law of the land.