A group of 40 U.S. senators have signed a letter opposing the Aderholt Amendment, which would allow child welfare agencies to discriminated against same-sex couples and others.

The amendment was added onto the House of Representatives’ funding bill for the Departments of Labor, Health and Human Services, and Education for the 2019 fiscal year, with all but one Republican on the House Appropriations Committee voting in favor of the discriminatory provision.

If enacted into law, the provision would allow child placement agencies to turn away prospective parents based on an agency’s religious beliefs.

The letter was addressed to Sens. Richard Shelby (R-Ala.) and Patrick Leahy (D-Vt.), the chairman and ranking member, respectively, of the Senate Appropriations Committee. In the letter, the 40 senators — all members of the Democratic Senate Caucus — promise to block the amendment from becoming a part of the final version of the appropriations bill.

The House bill has not yet been scheduled for floor debate. The Senate is expected to vote on its version in August. If the two bills continue to have different language with respect to the “right to discriminate” amendment, those differences will have to be resolved in conference committee.

LGBTQ and civil rights advocates have noted that the provision would not just harm LGBTQ people and same-sex couples wishing to adopt or foster children, but single parents, interfaith couples, and couples in which one partner has previously been divorced.

“We strongly encourage you to reject this language and instead, support federal laws and regulations barring discrimination, and protect the rights of all qualified parents who answer the call to foster and adopt children in foster care,” the senators write. “These children deserve the welcoming and loving homes that so many parents of diverse backgrounds are yearning to provide.”

The biggest barrier to finding suitable homes for children remains the lack of qualified prospective parents.

Statistics culled from in-depth research on the child welfare system suggest that an estimated two million LGBTQ adults are interested in adoption, but the LGBTQ community often remains an untapped resource when it comes to placing children with adoptive or foster families.

The Human Rights Campaign praised the senators’ actions, and called on Congress to remove the House amendment from the final version of the bill that emerges from the conference committee.

“The 40 U.S. Senators opposing the House’s ‘license to discriminate’ amendment see it for what it is: a blatant attempt to discriminate against LGBTQ people while disregarding what is in the best interests of children,” David Stacy, the director of government affairs at HRC, said in a statement. “As Congress continues to debate this funding bill, HRC urges Congress to reject any discriminatory amendment that would target LGBTQ people and harm tens of thousands of children waiting for loving homes.”