Lawmakers in the U.S. Senate have narrowly blocked a Republican party challenge to President Barack Obama's order that most employers or their insurers cover the cost of contraceptives.

The Democratic-led Senate defeated the measure by a vote of 51-48 Thursday. The Republican measure sought to allow employers and insurers to opt out of parts of the mandate they found morally objectionable. One Republican, however, voted with most Democrats to kill the amendment, and three Democrats voted in support of the measure, proposed by Republican Senator Roy Blunt of Missouri.

Religious groups, including Roman Catholic bishops in the United States, have strongly objected to the measure, saying it would force them to violate their beliefs and provide birth control for employees at religiously affiliated institutions, like hospitals and universities.

Supporters of the amendment said no religious organizations should be forced to violate the tenets of their faith. Opponents said the amendment would have allowed employers and insurers to deny coverage for any medical treatment for any reason.

The president's birth control coverage mandate originally exempted churches, but not religious institutions such as colleges and hospitals, from providing birth control to employees. Facing outrage from some religious organizations, the president quickly offered an accommodation that would exempt religious institutions as well. Most Republicans still think the health care law is an overreach by government.