The move signals a deeply split court on the issue of separation of church and state and proves "the justices are agonising over the issue the same way that people in society are," according to one US specialist in constitutional law.

"This tells us it's going to be a case by case decision, we don't have any clean cut rules, and context is everything," University of Cincinnati law professor Dr Ronna Greff Schneider told Ecumenical News International.

In the Texas case, the high court ruled 5-4 that a 6-foot [1.8 metre] monument on the grounds of the Texas state Capitol, positioned among other religious and historical displays, was a tribute to the nation's religious and legal heritage and did not constitute government endorsement of religion.

Chief Justice William Rehnquist wrote in the court's ruling: "No exact formula can dictate a resolution in fact-intensive cases such as this * The determinative factor here, however, is that 40 years passed in which the monument's presence, legally speaking, went unchallenged. And the public visiting the capitol grounds is more likely to have considered the religious aspect of the tablets' message as part of what is a broader moral and historical message reflective of a cultural heritage."

In the Kentucky case, the court ruled 5-4 that two displays inside courthouses did claim government endorsement of religion, which is unconstitutional.

The Kentucky case involved a dispute over two framed copies of the Mosaic law displayed in a courthouse. Justice David Souter wrote in the ruling, "The divisiveness of religion in current public life is inescapable. This is not the time to deny the prudence of understanding the establishment clause to require the government to stay neutral on religious belief, which is reserved for the conscience of the individual."

Professor Schneider said the court has struggled for more than 50 years "with the recognition that we are a religious people with religious traditions and balancing that with the need to keep church and state separate".

The United States House of Representatives, the lower house of the Congress, has a chaplain. US coinage includes the phrase "In God We Trust", and the Supreme Court begins its sessions with the phrase, "God save this honourable court".

All of this is accepted, Schneider said, yet the First Amendment of the US Constitution states, "Congress shall make no law respecting an establishment of religion," and the court has traditionally interpreted this to mean government actions must have a secular purpose, as argued in the Texas case.