Sen. Rob Portman likely will not support the Employment Non-Discrimination Act as it is currently written, according to a source familiar with the senator’s thinking.

Portman was the first Senate Republican to support gay marriage, when in March he revealed his college-aged son Will is gay. But Portman is concerned about the current ENDA language and has demurred in public when asked whether he could support the bill, introduced last month by a bipartisan group of senators led by Democrat Jeff Merkley of Oregon.

When asked Monday again about whether he would back the legislation, Portman said he was worried about potential lawsuits or impositions on religious groups that would occur if the law were enacted.

“I totally support the concept. This is about discrimination in the workplace. And there should be no discrimination and there ought to be a law in place, in my view,” Portman said Monday night at an event hosted by Buzzfeed. “The current version of ENDA that I’ve looked at, I have some concerns about. One, about the litigation that would result because it could be heavily litigated the way it is written.”

“Second is religious freedom, which is the point I’ve made all through this discussion on gay marriage as I’ve talked about it,” Portman continued. “I’m also a strong believer in religious freedom and I think an entity that has certain religious tenets should not be required to change those tenets because of this law or others. ENDA has traditionally addressed this issue and I’m sure they will.”

Portman’s office has been asking questions of the offices backing the current ENDA bill, according to sources on both sides of the aisle. But it’s unclear what changes will assuage the Senator and former GOP national ticket hopeful. Though he cited religious concerns as one of his two reasons for opposing the legislation, a copy of the bill text obtained by Roll Call suggests that religious protections are already built in:

SEC. 6. EXEMPTION FOR RELIGIOUS ORGANIZATIONS.

This Act shall not apply to a corporation, association, educational institution or institution of learning, or society that is exempt from the religious discrimination provisions of title VII of the Civil Rights Act of 1964 pursuant (42 U.S.C. 2000e et seq.) to section 702(a) or 703(e)(2) of such Act (42 U.S.C. 2000e-1(a), 2000e-2(e)(2)).