Department of Homeland Security Secretary Janet Napolitano on Wednesday defended a much-discussed remark recently made by President Obama that the U.S. "can absorb a terrorist attack," saying the U.S. has taken a number of actions to enhance security but "we can't seal the United States under a glass dome."

"I think what he meant is that we are resilient, we have absorbed terrorist attacks, we've absorbed a lot of other damage to our country and we always come back and will come back again," Napolitano told Fox News. "But again if someone were to get through, if an attack were to get through, we would recover efficiently and go after the attacker and come back as a country."

Obama made the statement to author Bob Woodward in his new book "Obama's Wars."

"We will do everything we can to prevent it, but even a 9/11, even the biggest attack ever, that ever took place on our soil, we absorbed it, and we are stronger," Obama is quoted as telling Woodward.

Some critics took the comment to mean that the U.S. isn't aggressive or ready enough for an attack. Even before the book was released, conservatives attacked Obama's use of the word "absorb."

"His statement demonstrates our commander-in-chief's cavalier and frightening approach to national security," reads The Heritage Foundation web site. Woodward added, "It would be like the head of Goldman Sachs going out and saying we can absorb another financial crisis."

Indeed, Woodward writes in "Obama's Wars" that he was "surprised" by the comment made during an Oval Office interview.

On Tuesday, he told Fox News' "The O'Reilly Factor" that he thought the remarks was "bizarre."

"I went to check to see if he had said that before. Turns out, he has not," said Woodward.

But Woodward said he understands Obama's frame of mind given the constant terror threat faced by the U.S.

"The president is living in a sea of warnings about future terrorist attacks," Woodward said. "He's trying to be realistic and lay the ground work for something that is going to happen. We've been lucky."

Napolitano's clarification comes as U.S. intelligence officials examine whether alleged terror plots targeting European cities signal a new threat to the United States. The homeland security secretary would not speak specifically to threats on the U.S. or western interests abroad, but called Al Qaeda a "determined adversary."

She added that homeland security is a shared responsibility that includes not just the U.S. government but citizens and local law enforcement.

Watch Woodward's interview with O'Reilly below.