Updated

A GOP lawmaker is seeking answers from the Obama administration on how it plans to combat the potential radicalization of Americans now in Yemen -- a country that has come under the thumb of Al Qaeda.

Rep. Frank Wolf of Virginia said about 55,000 Americans are visiting, living or studying in Yemen along with other Westerners -- a figure he received from the State Department, which told FoxNews.com that the majority of those Americans have dual citizenship and some of them may never have been to the U.S.

In a letter to Obama's top counterterrorism adviser, John Brennan, Wolf asked for an analysis on how many of those Americans are subject to radicalization and how the administration is planning to deal with converts who can fly back to the United States with American passports.

"This is especially troubling in light of the fact that the Yemeni government does not control large portions of the country outside of the capital city," he wrote.

The National Security Council did not immediate respond to an e-mail seeking comment.

Wolf's inquiry stems from the failed Christmas Day airliner bombing by an accused Nigerian who says he received training from an Al Qaeda affiliate in Yemen. Yemen has since become a focal point for counterterrorism officials.

One senior Democratic senator urged the U.S. Wednesday to consider air strikes and other clandestine operations in Yemen to defeat a resurgent Al Qaeda force there.

Sen. Carl Levin, chairman of the Senate Armed Services Committee, said in a conference call with reporters that "most options ought to be on the table" with the exception of a U.S. invasion of Yemen.

"I think that these are proven threats to the United States, and if we identify them, it's appropriate for us to act against them," he said.