Homeland Security says airlines must step up security for US-bound flights or face possibility of total electronics ban.

Authorities in the United States have unveiled tough new security measures for international flights arriving in the country, but held off from a threatened expansion of a carry-on laptop ban.

The Homeland Security Department said on Wednesday it would now require enhanced screening of personal electronic devices, passengers and explosive detection for the roughly 2,000 commercial flights landing daily in the US from 280 airports in 105 countries.

Officials said the agency would issue directives to about 180 air carriers, including US airlines.

“Security is my number one concern,” John Kelly, secretary of homeland security, said during a speech at the Center for a New American Security. “Our enemies are adaptive and we have to adapt as well.”

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Kelly said the changes will be “seen and unseen” and will be phased in over the coming weeks and months.

He said airlines that do not comply or are slow to enforce the new standards could be forced to bar large electronics from both carry-on and checked luggage. They could also lose permission to fly into the US.

The current ban, which affects only foreign carriers flying to the US from 10 cities, allows passengers to travel with larger electronics packed in checked baggage.

The original laptop and electronics ban has been in place since March amid concerns about an undisclosed threat described only as sophisticated and ongoing. That ban applied to nonstop flights to the US from Amman, Jordan; Kuwait City, Kuwait; Cairo; Istanbul; Jeddah and Riyadh, Saudi Arabia; Casablanca, Morocco; Doha, Qatar; and Dubai and Abu Dhabi in the United Arab Emirates. The roughly 50 affected flights are on foreign airlines.

The government had considered expanding the laptop ban to include some European airports, though in recent public comments Kelly had suggested the government was looking at alternatives.

Al Jazeera’s Shihab Rattansi, reporting from Washington, DC, said the specifics of the new security measures were unclear.

“The specifics are a little vague and the Department of Homeland Security says that’s on purpose because they don’t discuss security measures in public,” he said.

“What we understand is that if an airport wants to avoid a laptop ban, it has to enhance its security, including the checking of electronic devices for explosives and the screening of passengers and airport workers.”

Questions over new measures

Kelly also said the US would push harder for foreign airports to accept “pre-clearance” immigration operations manned by US Customs and Border Patrol officials to process US-bound passengers before they board their flights.

Such operations have already been established in 15 locations in six countries, including Canada, Ireland and the United Arab Emirates.

But it raises sensitive sovereignty issues to have US law enforcement officials operate inside another country.

READ MORE: US electronics ban for Middle East flights draws doubts

US officials remained vague about the specific requirements of the new programme.

Airlines will be pressed to adopt a mix of new measures, including installing new screening technology, making more use of chemical sniffer dogs, and other unspecified steps.

But the precise requirements in each case would depend on individual airlines, the airports they fly from, and their current levels of security. Some will have to make only minor improvements, they said.

Asked about timeframes, officials would only say that they would give adequate time for the airlines to adapt.

“We are raising the bar globally” for security standards, one senior official, who declined to be identified, told the AFP news agency.

They also said they expect nearly all carriers to be able to meet the new standards.