Former U.S. Sen. Rick Santorum has joined a conservative Washington think tank where he will found and direct a program called "America's Enemies."

The program will study "threats posed to America and the West from a growing array of anti-Western forces that are increasingly casting a shadow over our future and violating religious liberty around the world," according to a statement from the Ethics and Public Policy Center, where Mr. Santorum will be a senior fellow.

"In these perilous and uncertain times, I believe it is critical that we define the threats that confront America," Mr. Santorum said in a prepared statement.

He did not respond to interview requests.

"Without a clear definition and precise understanding of our enemies we cannot fight effectively and our own citizens become divided," he said. "It is my hope that the America's Enemies program at EPPC will help the American people -- including our leaders -- understand and communicate with clarity, honesty and consistency the enemies we face and the complex and enormous threat that they pose to our lives and the freedoms we all enjoy."

The center was established 30 years ago to apply moral principles derived from Judaism and Christianity to issues of public concern. It is best known for its Catholic scholarship, although it also has expertise on evangelicalism and a Jewish studies program. Mr. Santorum, who served in the Senate from 1995 until this year, is a devout Catholic.

He lost his Senate seat in November to former state Treasurer Bob Casey.

Mr. Santorum is a good fit for the center, said its president, M. Edward Whelan III.

"Our mission is to explore how the Judeo-Christian moral tradition applies to public policy. And there is no issue more pressing than that which radical Islam poses," he said.

Mr. Santorum has spoken frequently on what he calls "Islamic fascism" as the primary threat to the United States. In an article for Crisis magazine, he defined it as "a radical, perverted form of Islam" that seeks world domination.

In the same article, he wrote that other Muslims should share his concern because "Islamic fascism produces the systematic murder of innocents, including many Muslim innocents."

He elaborated on that in a Dec. 6 speech on the Senate floor, opposing the nomination of Robert Gates as secretary of defense.

"When I stepped forward to define the enemy as radical Islamic fascists, I was ridiculed by the media and others, saying that my words were too harsh, saying that at worst my defining the enemy was incorrect, at best it was inflammatory. But I did so because I believe words matter. If you are going to confront an enemy you have to understand who that enemy is and you have to communicate that to the people of America," he said.

But he argued that the key to countering radical Islam was support for other Muslims who support religious liberty and human rights.

"We cannot defeat radical Islamic fascism. The only thing we can do is, through democracy-building and through support of moderate Islam, give those who truly seek ... the true moderate meaning of Islam the opportunity to be successful in suppressing its radical elements," he said.

The center has had a program called Islam and American Democracy, which studied the political views of American Muslims and featured Muslim speakers who favored pluralism and democracy.

But that program lost steam when its director left, Mr. Whelan said.

"The time of war is not the time to be irenic. And Rick's program will focus on radical Islam, not on Islam," he said.

Corey Saylor, national legislative director for the Council on American Islamic Relations, expressed concern about the program, and criticized Mr. Santorum's prior discussion of radical Islam.

The term "Islamic fascism" is "a ridiculous attempt to link Islam with one of the worst horrors of the 20th century. Islam had nothing to do with fascism," he said.

"It's a rhetorical term that doesn't define any problems or solve any problems."

Mr. Saylor said he hoped Mr. Santorum would engage with American Muslim organizations and their constituencies.

"That way he can learn more about the faith from the people who are practicing it and who represent large groups of Muslims," he said.

"We think that might help reshape some of his ideas, particularly in the viability of the term Islamic fascism."