Trump unveiled the federal government's first updated guidance on school prayer since 2003, at an Oval Office event joined by Education Secretary Betsy DeVos,

It details scenarios in which school officials must permit prayer and clarifies the consequences if they don't, but overall it makes few major changes to the guidance it replaces.

"We will not let anyone push God from the public square," Trump said as he introduced the new rules. "We will uphold religious liberty for all."

Trump has given the evangelical constituency greater attention in recent weeks following a Christian magazine's call for his removal from office.

By rallying around school prayer, Trump is rekindling a debate that reached a crescendo in the 1980s and '90s but has fallen to the periphery of national politics. Trump argued that it needs new attention as schools increasingly go too far in restricting prayer.

"You have things happening today that 10 or 15 years ago would have been unthinkable," he said in response to a question about his views on culture war. "Taking the word God down, taking the word Christmas out. I think we've turned that one around very good. I think we've turned both of them around very good."

Public schools have been barred from leading students in classroom prayer since 1962, when the Supreme Court said it violated a First Amendment clause forbidding the establishment of a government religion. Later decisions placed restrictions around prayer at graduation ceremonies and athletic events.

Civil liberties groups say the firewall protects religious minorities and ensures equal treatment of all faiths. But many on the Christian right say courts and schools have swung too far against prayer and now interfere with the right to free religious expression.

Michael Farris, CEO and general counsel of the legal advocacy group Alliance Defending Freedom, called Trump's new school prayer guidance a "welcome step to remedy these attacks on people of faith."

Australian Associated Press