Senate Democrats and the White House are drawing a line in negotiations over the defense authorization bill, signaling strong opposition to a provision they say would allow for discrimination based on sexual orientation and gender identity.

The issue has emerged as one of the hurdles in the negotiations over the National Defense Authorization Act. An amendment added to the House version of the bill would expand protections and exemptions to “any religious corporation, religious association, religious educational institution, or religious society” that receives a federal contract.

White House Chief of Staff Denis McDonough has personally reached out to key lawmakers on the issue, administration officials said at at a Monday meeting with stakeholders.

Meeting participants who spoke to CQ on the condition of anonymity said President Barack Obama is prepared to veto the fiscal 2017 defense policy bill over that language, should it reach his desk.

Senate Democrats argue that the amendment could upend Obama’s executive order barring federal contractors from discriminating against lesbian, gay, bisexual and transgender individuals.