Pennsylvania lawmakers will introduce a state constitutional marriage amendment this week that will define marriage as the union of one man and one woman.

The amendment will also prevent recognition of out-of-state same-sex marriages.

Nearly 90 co-sponsors in the 203-seat House of Representatives have signed on.

The Center for Lesbian and Gay Civil Rights in Philadelphia is mobilizing an effort to defeat the bill, saying it's writing discrimination into the state constitution.

The earliest voters would be able to cast a ballot is 2007.