New airport security measures

• NEW: "Our job is to ... try to anticipate the next attack," Jeh Johnson tells NBC


• TSA may require passengers en route to United States to turn on their electronics


• They want to make sure the devices work and aren't explosives


• It's part of a series of new measures aimed at combating potential new threats overseas

Washington (CNN) -- Power it up, or leave it behind.

The Transportation Security Administration said Sunday that security screeners at overseas airports may ask U.S.-bound passengers to turn on their electronic devices to prove they work and aren't explosive devices.

They won't allow devices without power on board planes. The traveler may then undergo additional screening.

It's part of an update to security measures aimed at combating potential new threats from terrorists in the Middle East and Europe.

What caused new airport security moves?

Secretary of Homeland Security Jeh Johnson directed the TSA last week to enhance security at overseas airports that have direct flights to the United States. The specifics of the enhanced measures weren't originally released, and it isn't known what other measures the TSA may employ.

The TSA also would have to coordinate with the foreign governments which provide security at airports in their countries, along with the airlines and private security companies.

"Our job is to ... try to anticipate the next attack, not simply react to the last one. And so we continually evaluate the world situation, and we know that there remains a terrorist threat to the United States, and aviation security is a large part of that," Johnson told NBC's "Meet The Press."

"This is not something to overreact to or over-speculate about," he said.

A homeland security official said last week that the changes would primarily focus on airports in Europe and the Middle East.

The effort does not involve changes to what travelers can take aboard flights. But passengers may see additional inspections of shoes and electronics, additional use of scanners designed to detect trace amounts of explosives, and another stage of screening at boarding gates, in some cases, the official said.

The changes came about based on new intelligence on terror groups trying to build new types of improvised explosives that are harder to detect, the official told CNN.

While there was no specific threat prompting the enhancements, U.S. officials are concerned about the possibility that al Qaeda in the Arabian Peninsula might develop bombs which could pass through current security measures undetected.

Since hardening cockpit doors and taking other measures after the 9/11 al Qaeda attacks, the U.S. aviation security focus has shifted primarily from hijackings to plastic and other explosives that can be carried aboard a plane or hidden in baggage.

The UK Department for Transport confirmed Wednesday that it is stepping up some of its aviation security measures.

"For obvious reasons we will not be commenting in detail on those changes. The majority of passengers should not experience significant disruption," a spokesman said.

"The UK has some of the most robust aviation security measures, and we will continue to take all the steps necessary to ensure that public safety is maintained."

The updated security measures only apply to airports overseas, and Johnson said he doesn't think the enhancements will make their way to domestic airports at this time.

"I believe that we've taken the appropriate measures to deal with the existing situation and not unnecessarily burden the traveling public," Johnson told NBC.

Tighter security ordered for some U.S.-bound flights

CNN's Jim Sciutto and Evan Perez contributed to this report.