Nearly 20 Democratic senators and 80 members of the House of Representatives signed sharply worded letters that were sent to Secretary of State Mike Pompeo on Thursday, calling on his department to reverse a policy that has been used to deny citizenship to children of Americans born abroad through assisted reproductive technology.

The two letters, which criticized the State Department’s position as “cruel,” “offensive” and “deeply disturbing,” are the latest escalation in tensions over a longstanding citizenship policy that has recently come under scrutiny for its effect on same-sex couples.

Under State Department policy, children born abroad must have a biological connection to an American parent to receive citizenship at birth. That is not a problem when couples have babies the traditional way, but can prove tricky when couples — particularly gay and lesbian couples — have children through techniques like surrogacy and in vitro fertilization, if only one spouse is the genetic parent.

Because the department focuses on biological parentage, certain assisted reproductive technology cases are treated as “out of wedlock,” even if the child’s legal parents are married. That designation triggers a higher threshold for transmitting citizenship, which can include additional residency requirements for the parents that might not apply if the child had been born without reproductive help.