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 he will be a senior fellow.

The center was established 30 years ago to apply moral principles derived from Christianity and Judaism to public policy issues. It is strongly, but not exclusively, associated with conservative Catholic intellectuals. Another of its senior fellows, George Weigel, is best known as the author of the most comprehensive biography of the late Pope John Paul II. Mr. Santorum, who served as a Pennsylvania senator from 1995 until this year, is an outspoken Catholic.

"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.

"Without a clear definition and precise understanding of our enemies we cannot fight effectively and our own citizens become divided. 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 post to our lives and the freedoms we all enjoy."

Mr. Santorum has spoken previously on what he called "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.

Some of the center's other programs include Evangelicals in Civic Life, Economics and Ethics, Jewish Studies and Islam and American Democracy. The latter studies the views and impact of American Muslims and seeks to give a platform to pro-democracy reformers within Islam.