Passengers flying to the US face tighter vetting and "enhanced screening" of large electronic devices, such as laptops and iPads, Washington announced last night.

Amid fears that the new controls could lead to delays at airports, passengers are being advised to allow additional time to clear check-in and security screening.

According to the latest figures, more than four million Britons travel to the US each year.

The tighter controls unveiled by John Kelly, the Homeland Security Secretary, will apply to the estimated 280 airports in 105 countries - offering flights to the United States.

Countries which fail to meet standards set by Washington could see flights to the US suspended completely.

The US imposed a ban on large electronic devices on flights from 10 Muslim-majority countries in March.

But Washington's plans to extend the ban to other countries including members of the European Union has faced resistance from both Brussels and the aviation industry.

Faced with the impasse Mr Kelly has ordered all airports serving the US tighten security, threatening strict sanctions on countries who fail to comply.

The new measures will be "seen and unseen", the US Department of Homeland Security said.

"Those who choose not to cooperate or are slow to adopt these measures could be subject to other restrictions—including a ban on electronic devices on their airplanes, or even a suspension of their flights to the United States," he said.