Former Pennsylvania Sen. Rick Santorum will take another step toward a likely presidential campaign when he delivers a sweeping foreign policy speech at the National Press Club in Washington, D.C., on April 28.

In the speech, entitled "America and the World: Resetting Our Course," Santorum will outline his criticisms of the Obama administration's "confusion" on the world stage while conveying his own vision of the United States' role in the world.

One of Santorum's most daunting challenges as he has laid the groundwork for a likely presidential run has been to convince voters and the media that his reach extends beyond an appeal to social conservatives.

As a senator who was so closely identified with his outspoken views on hot-button issues like abortion, homosexuality and intelligent design during his two terms in office, Santorum carries certain advantages in the evangelical-heavy first caucus state of Iowa.

But early polls have shown that the former senator who lost his 2006 re-election battle has a lot of work to do in order to make the case that he would be a multidimensional candidate who could appeal to a broad swath of the Republican electorate.

Foreign policy is one area where the formed Armed Services Committee member may be able to separate himself a bit from a field that will likely be crowded with former and current governors.

"Looking at the current field, Rick Santorum is the only prospective candidate with foreign and defense policy experience based on his Senate and House career," a Santorum aide told RCP. "Having served eight years on the Senate Armed Services Committee and focusing on these issues since he left office in 2007, Sen. Santorum has seen a steady erosion of our commitment to our own national security as threats from the Middle East to our own backyard to domestically have only increased."

Though domestic issues almost always take precedence in nominating contests, Santorum could earn a certain gravitas quotient by highlighting his years in the thick of key policy debates over international crises from the Balkans to Iraq.

The recent uprisings in North Africa and the Middle East have served as reminders of how unpredictable foreign events can suddenly take center stage in the post-9/11 world, and each Republican candidate will have to make the case that he or she is best-equipped to go toe-to-toe against an incumbent president with whom Americans have become familiar as an international leader.

Mississippi Gov. Haley Barbour has already sought to differentiate himself from the field by voicing skepticism over the role of U.S. troops in Afghanistan, and Ambassador to China Jon Huntsman is likely to show off his unique expertise as he gears up for his own likely White House run next month.

Santorum's speech could generate additional attention if he goes beyond the usual anti-Obama talking points and breaks from the Republican pack on a key international issue.

An aide said that aside from outlining his broad foreign policy approach, Santorum will also speak about his views on the "moral foundations of our foreign and defense policy" -- a nod to his culturally conservative base of support.