On the eve of the busiest travel days of the year, US officials were scrambling Tuesday to ease passenger worries amid a national uproar over revealing full-body scans and invasive pat-downs.

Top US aviation security official John Pistole said Monday he was open to making body searches less uncomfortable for passengers, and the White House said the system, aimed at boosting security during an ideal target time for attacks, would "evolve."

But the row over pat-downs showed no signs of ebbing, ahead of the Thanksgiving holiday that traditionally sees hordes of Americans crowd airports, roads and railways. The holiday officially takes place on Thursday, but nightmarish travel lasts Wednesday through Sunday.

Pistole, head of the Transportation Security Administration (TSA), said he had agreed to consider how to conduct this type of screening "less invasively."

"That has been the request (and) I'm open to doing that," he told Fox News, vowing to work to find "less intrusive means" that still provide reliable screening data.

But Pistole insisted the new measures put in place earlier this month will not be scrapped so long as the security threats remain.

And the TSA said that less than three percent of passengers are subjected to pat-downs, which only occur if passengers opt out of full body X-rays, which many passenger say are too revealing.

"There is a continued threat against aviation involving those who seek to smuggle powders and gels that can be used as explosives on airplanes," Homeland Security Secretary Janet Napolitano said. "The new technology is designed to help us identify those individuals."

A new Washington Post/ABC News poll found that nearly two thirds of Americans support the scanning machines, putting greater emphasis on the governmen fight terror than focusing on personal privacy.

But half of those polled said they thought the intimate pat-down searches "go too far."

They were also concerned that the enhanced security measures would further lengthen already long lines at the airport.

At the White House, President Barack Obama's spokesman appeared to hint that there might be changes to the system, but took care to avoid tipping off potential attackers on US security procedures.

"Our charge is to do all that we can to protect those that travel, but also to do so in a way that's... minimally invasive," said Robert Gibbs. "That's a balance that we will continue to search for."

"We seek to maximize the security and protection and minimize that invasiveness. These are procedures that will continue to evolve."

But he stressed that security measures had been put in place specifically to address threats from Al-Qaeda, though declined to go into details to protect the integrity of the process.

"We know from intelligence that Al-Qaeda seeks to do harm through aviation, through devices concealed on a body, inside of a device that one might take on to an airplane or in luggage that's put on an airplane."

Critics complain that agents use their fingers and open palm uncomfortably close to the genital area during the pat-downs.

During the body searches, female agents run their hands between and under women's breasts and both sexes are patted down from crotch to ankles, front and back. Agents can only search passengers of the same sex as their own.

Pistole reminded the public that the measures were implemented to plug perceived holes in aviation security at a time of growing terror threats.

The more intimate pat-downs and full body scanners were introduced in the wake of a string of foiled bomb plots against US-bound airliners.

Those include the Christmas Day bomb attempt last year when Abdul Farouk Abdulmutallab, a young Nigerian, allegedly tried to ignite plastic explosives concealed in his underwear as his plane came in to land in Detroit.

Pistole acknowledged US officials were caught off guard by the extent of the public outrage against the measures.

"I think it's safe to say there has been a reaction that not many people could have predicted, including myself," he said.