A Christian university in Arizona has granted benefits to lawfully married same-sex couples while maintaining its religious beliefs that marriage should be between a man and a woman.

The Grand Canyon University (GCU) in Phoenix said its decision respects the government and laws after the U.S. Supreme Court legalised same-sex marriage in the country last June.

"As a result, notwithstanding GCU's sincerely held religious beliefs regarding marriage, we have recently been confronted with the issue of whether GCU will extend benefits to lawfully married same-sex couples. For the reasons articulated in this statement, in this specific instance, GCU is making a conscious choice to maintain its religious beliefs, while respecting and honouring its neighbours, as well as the system of government and laws that exist today, by extending employee benefits to spouses of lawfully married same-sex couples," the university said in a statement.

It clarified that this does not change its stance on marriage.

"To be clear, though, the University's decision in this instance, and the recent changes, or any future changes, in the government's definition of marriage, do not, and will not, change GCU's sincerely held religious belief that marriage is a sacred union between a man and a woman," it said.

GCU said this sacred union between a man and a woman will continue to be espoused throughout the University's curriculum and classrooms. "This belief is not negotiable," it said.

The university, which has about 16,000 students, was earlier criticised by its employees for denying benefits to same-sex couples, the Gospel Herald reported.

The American Civil Liberties Union (ACLU) in Arkansas told the university that it was violating federal laws. An employee filed a complaint.

"This is an important win for everyone involved," said Victoria Lopez, the ACLU chapter's legal director. "People should not be discriminated against because of who they are, who they love and who their families are."

The university said, "Some may judge GCU harshly for its decision to remain firmly rooted in traditional Christian convictions and steadfast in its commitment to the biblical view of marriage. Others may chastise the University for extending benefits to same-sex spouses because the decision can be misperceived as an implicit endorsement of non-Christian views."

"Both responses would fail to comprehend GCU's position adequately. The decision to remain consistently Christian and profoundly biblical remains a legitimate, constitutionally-protected position. This position is neither intrinsically harsh nor unloving, no matter how unpopular it has become in some circles," it said.