Clinton signed orders which ended the ban on Professor Tariq Ramadan of Oxford University, who was barred due to alleged terrorism ties which he denies, State Department spokesman P.J. Crowley said on Wednesday.

He added that the ban had also been lifted for Adam Habib of Johannesburg University, another prominent Muslim scholar.

"As we look at it, we do not think that either one of them represents a threat to the United States," Crowley told a news briefing, adding that the U.S. government hoped to encourage more interaction with the Muslim world.

"We want to encourage a global debate. We want to have the opportunity potentially to have Islamic scholars come to the United States and have dialogue with other faith communities in our country," he said.

He added that both men would still be subject to regular standards that apply if they put in new U.S. visa requests.

Ramadan, speaking in London, said the decision showed what he called a new U.S. willingness to permit critical debate while the American Civil Liberties Union said it was an important move.

"The orders ending the exclusion of Adam Habib and Tariq Ramadan are long overdue and tremendously important," said Jameel Jaffer, Director of the ACLU National Security Project, saying this was "a major victory for civil liberties."

"For several years, the United States government was more interested in stigmatizing and silencing its foreign critics than in engaging them. The decision ... is a welcome sign the Obama administration is committed to facilitating rather than obstructing the exchange of ideas across international borders."

Ramadan, who has Swiss citizenship, told Reuters that as a result of the decision he would apply soon for a visa to visit the United States.

Civil liberties campaigners have championed the cases of Ramadan and Habib as part of a pattern of scholars and writers being excluded due to unwarranted or unspecified U.S. national security grounds.

The United States has revoked Ramadan's visa several times since 2004. Washington initially gave no reason for its decision, but later said Ramadan had been barred based on a provision of the USA Patriot Act that allows people to be excluded for supporting terrorism.

The ACLU argued the government was using the provision more broadly to deny entry to people whose political views it did not approve of.

Habib was detained and interrogated about his political views and associations when he arrived in New York in October 2006 for meetings with groups such as the World Bank and ACLU.

In an interview, Ramadan told Reuters he remained barred from several Arab countries including Egypt and Saudi Arabia and he had little hope these bans would be lifted any time soon.

Ramadan said he was unpopular with some Arab governments because he had criticized them for what he described as failing to support the Palestinian people and seeking to place the responsibility for the Palestinians' situation on the West.

(Reporting by Andrew Quinn in Washington and William Maclean in London, Editing by Ralph Boulton and Vicki Allen)