In a notable shift, Republican senators voted unanimously against a proposal to expand the military’s coverage of fertility treatments.

Republicans in Congress have quietly blocked a proposal to expand military health coverage of in vitro fertilization treatment for service members and their families, heeding the calls of anti-abortion groups to limit access to a fertility option that President Trump vowed to make more widely available.

The move is a shift from previous years, when there was enough bipartisan support for the idea of broadening the availability of I.V.F. for members of the military that it was included in the annual defense bill that passed both the House and Senate. 

During a closed-door meeting of the Senate Armed Services Committee last month to draft the defense bill, all 14 Republican senators voted against adding the I.V.F. coverage provision, offered by Senator Tammy Duckworth, Democrat of Illinois.

The military currently covers the treatments only for active-duty service members whose infertility was caused by an injury or illness sustained in the line of duty. Ms. Duckworth’s proposal would make it available to other service members and their families.

The closed-door vote afforded Republican senators a chance to privately signal to those groups and the conservative voters who vehemently oppose I.V.F. that they are aligned.

This year, no Republican proponent spoke up, the people familiar with the session said, and there was no debate beyond the reading of SBA Pro-Life America’s position.

The vote took place after Senator Dan Sullivan, Republican of Alaska, proposed an amendment that would have barred the Defense Department from paying for pre-implantation testing of embryos and required that all embryos created in a cycle be implanted. 

But Mr. Sullivan’s amendment, which had the backing of some anti-abortion rights organizations, was withdrawn at the last minute and the committee instead proceeded to kill Ms. Duckworth’s provision.

Mr. Sullivan’s office declined to comment.