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The chairman of the Senate Homeland Security Committee -- who has blasted the Obama administration for its handling of recent terrorism cases -- came to the defense of the administration on Tuesday, amid a growing furor over the use of advanced imaging technologies and pat-downs at U.S. airports.

"I support every one of those steps we've taken," Sen. Joe Lieberman, I-Conn., told Transportation Security Administration chief John Pistole during a hearing on air safety. "I think that perhaps the reaction to the pat-down procedures got ahead of TSA's or the [Department of Homeland Security's] description of what you were doing and why you were doing it. If God forbid that bomb on [Christmas Day] had gone off on the plane over Detroit, Congress and -- I dare say -- the public would have been demanding not just the body imaging equipment but pat-downs."

This comes three days after a California wan was forced to leave San Diego's airport for refusing to let security officers use full-body imaging or pat him down, telling them, "If you touch my junk, I'll have you arrested."

The video of the incident, captured on the man's cell phone, has become an online hit. At the same time, critics have launched an "opt out" campaign online, calling on those traveling the day before Thanksgiving to refuse full-body imaging, which would force TSA agents across the country to give pat-downs and, organizers say, would let Americans "see for themselves how the TSA treats law-abiding citizens."

Pistole acknowledged such developments have created "a lot of publicity," but he said terrorist plots are "ever-evolving" and the U.S. government has a "challenge" to develop "the best techniques and tactics enabled by the best technology to detect those plots" while being "sensitive to people's concerns about privacy."

"We recognize -- I particularly recognize -- that reasonable people can disagree as to what that proper balance or blend is between privacy and security and safety," Pistole said. "That being the case, I think everybody who gets on a flight wants to ensure and be ensured that everybody else around them has been properly screened. ... What I am concerned about, and I know many share this concern, is if we have an individual who opts out of the advanced imaging technology ... thinking, 'Well, I am not going to receive a thorough pat-down so i can get on that flight.'"

Pistole said he believes advanced imagine technology is "the best technology we have today to detect a non-metallic device that [is] well-designed and well-concealed," like the one 23-year-old Umar F. Abdulmutallab of Nigeria tried to detonate over Detroit last Christmas Day.

Lieberman told Pistole that while full-body scans may be intrusive and pat-downs are "awkward," "unusual" and "sensitive," he thinks they are "necessary for the homeland security of the American people," and the U.S. government is "doing the right thing"

"We get on those planes, and we want to have the confidence that nobody on the plane has evaded security in a way that will allow them to blow up the plane and kill everybody else on it," Lieberman said. "This is unfortunately the world in which we live. It wasn't our choice, but we have to do everything we can to protect the traveling public."

The ranking Republican on the Senate Homeland Security Committee, however, said she still "remains concerned about the intrusiveness and effectiveness of the advanced imaging technology and the potential negative health effects."

"Obviously our government's first priority is to protect our people against terrorism, and the public will expect a certain level of intrusion and inconvenience," Sen. Susan Collins, R-Maine, said. "But DHS should be using technology and techniques that are as safe and effective as possible [and] that minimize privacy concerns whenever possible."

She called on DHS, which oversees TSA, to conduct an independent evaluation of the health effects of full-body imaging machines. Some have raised concerns about repeated exposure to radiation, and when 31-year-old John Tyner arrived at San Diego International Airport on Saturday for a hunting trip in South Dakota, he had already read extensively about full-body imaging machines and "the possible harm to health as well as the vivid pictures they create of people's naked bodies," according to a posting on his blog.

On Monday, Homeland Security Secretary Janet Napolitano said the effects of such machines "have been examined six ways to Sunday" by governmental and non-governmental entities, and they found the radiation involved is "almost immeasurable, it is so small."

Still, after TSA agents directed Tyner to a full-body imaging machine on Saturday, he refused, prompting one TSA agent to tell him he would have to undergo a pat-down.

"After he described the pat down, I realized that he intended to touch my groin," Tyner wrote on his blog within hours of the incident. "Before he started the pat down, I looked him straight in the eye and said, 'If you touch my junk, I'll have you arrested.'"

Authorities subsequently told Tyner he couldn't leave the airport without completing the screening because he "may have an incendiary device and whether or not that was true needed to be determined," Tyner wrote on his blog.

Tyner recorded much of the incident on his cell phone, and the subsequent video has been viewed by hundreds of thousands online.

TSA announced on Monday it was launching a formal investigation into the incident, and Tyner could face prosecution and civil penalties up to $11,000.

On Tuesday, Pistole suggested people who have seen the video should focus on the actions and motivations of the TSA officers involved.

"I think if people get away from just the passenger [Tyner] to hear what the security officer was saying, he was very cool, calm, professional, and that's what we expect of our security officers," according to Pistole.

Pistole said the "bottom line" is that if passengers could choose whether to fly on a plane where "everybody has had a thorough screening" or one "where we have not done a thorough screening because people didn't feel comfortable with that, I think most if not all of the traveling public will say I want to go on that plane that has been thoroughly screened."

Nevertheless, several websites are calling for a national "Opt Out Day" on Nov. 24, insisting many Americans "only fly around the holidays and may not be aware of the security changes."

"The government should not have the ability to virtually strip search anyone it wants without cause," says the website OptOutDay.com. "We do not believe the government has a right to see you naked or aggressively touch you just because you bought an airline ticket. ... Once people are made aware of what is happening, they may have reservations about the new virtual strip searches and enhanced pat downs -- especially for their children or spouse or other loved one."

Pistole said only "a small number or percentage" of passengers receive pat-downs, with the procedure occurring "almost exclusively in a situation where somebody has opted out of the advanced imaging technology or they have alerted on that because there is something still in their pocket or they may be trying to carry some contraband."

During a press conference on Monday, Napolitano said TSA and her department act responsibly "with good intelligence, with risk-based analysis," adding that "everybody has a role to play" in preventing terrorism "and if people don't want to play that role, if they want to travel by some other means, of course that's their right."

At the Senate hearing on Tuesday, asked by Lieberman whether he had any "final" thoughts, Pistole said he would like to "appeal to the people" traveling before Thanksgiving to "really look at this as a partnership" with the U.S. government and "try to be patient, work with our folks."

"They are there to protect you and your loved ones," Pistole said.

There are currently hundreds of advanced imaging technology units at airports around the United States. According to TSA and DHS, an officer located away from the security line views a slightly blurred, X-ray-like image of a passenger, but the officer does not see the passenger. The image cannot be stored, transmitted or printed, and is deleted immediately once viewed, authorities have said.