Homeland Security Secretary Michael Chertoff says his top priority, following the uncovering of an airplane terror plot in Britain, is to learn if the plotters have any links to people in the United States.

Homeland Security Secretary Chertoff was the lead guest on most major television talk shows Sunday. He told CBS' Face the Nation his agency's number-one priority is finding out whether there are any U.S. connections to last week's foiled terror plot in Britain.

"As we speak right now, we have not found any indication of active planning in the U.S., or plans to conduct operations within the U.S," said Michael Chertoff. "But as new information comes in, literally every hour, that is going to the main thing we are looking at."

British authorities arrested more than 20 people last week, on suspicion of being part of a plot to blow up multiple commercial aircraft with liquid explosives. Chertoff told NBC's Meet the Press he believes British officials have, in his words, "scooped up" the "main elements of the plot."

"We do not know, however, if there [are] some lines [connections] that lead into pockets [groups of people] that have not yet been arrested," he said. "We also have to be mindful of other groups that may think they have an opportunity to exploit our focus on this plot in order to carry out their own plots."

Chertoff did not make any definite accusations. But he added that the uncovered plot in Britain has what he described as the "hallmark" of an al-Qaida plot, in terms of sophistication and scope.

The al-Qaida terror network masterminded the September 11, 2001 terror attacks in the United States, which involved four simultaneously hijacked commercial airplanes. Since then, Chertoff said the United States has moved against al-Qaida, including killing or capturing many of the group's leaders.

The ranking Democrat on the House of Representatives' Select Intelligence Committee, Jane Harman, told CBS she is concerned that other would-be terrorists also may choose to imitate al-Qaida.

"Well, al-Qaida's been substantially degraded at the top," said Jane Harman. "But as we have learned, it's a multi-headed Hydra [a mythological creature], and it grows new heads. And with these copycat cells, who are inspired by al-Qaida, not necessarily directed by al-Qaida, the world is more dangerous."

This concern was also raised by Tom Kean, the Republican chairman of the 9/11 Commission, which examined the September 11 al-Qaida terror attacks. He called the recent events in Britain a wake-up call.

"I think there are a whole bunch of things happening in the world which has tended to make Muslims dislike the United States more than they even did before," said Tom Kean. "After 9/11, there was certain world sympathy that came to us. Since then, the war in Iraq, our support for Israel, which is constant."

He added that one fundamental problem is how to deal with what he and commission co-chair Lee Hamilton called the radicalization of Muslims in the world today. Many of the people who become terrorists, he said, are poor, unemployed and without hope of a better life.