Congress is considering passage of the first major civil rights act protecting gays and trans-sexuals.
The Employment Non-Discrimination Act, or ENDA, prohibits workplace discrimination based on sexual orientation and gender identity.
Critics said ENDA would impose its provisions on business owners who have religious objections to hiring gays and trans-sexuals.
Ashley Horne, federal issues analyst for Focus on the Family, said her ministry would fight the bill.
"It's definitely a bill we will put a lot of resources toward fighting," she said. "Our primary concern is the chipping away of religious liberties."
Jim Campbell of the Alliance Defense Fund, a Christian legal group, said there is a long-term strategy in the bill.
"One of the really big problems with enacting ENDA is in the future litigation battles dealing with same-sex marriage," Campbell said. "It will provide ammunition for homosexual activists in the future to push their agenda in the court system throughout the country."
However, supporters of the measure said religious organizations, the military and businesses with less than 15 workers are exempt.
"We're further than we've ever been, but there is certainly still work to be done," said Joe Solmonese, president of the Human Rights Campaign.