The US is to start charging UK travellers nearly £10 to apply for permission to enter the country.
From September 8, people will have to pay 14 dollars (£9) to use the compulsory Electronic System for Travel Authorisation (Esta). Of the fee, 10 dollars will apparently go to a fund to promote US tourism with four dollars covering administration.
The Esta form takes up to 72 hours to be approved and gives air passengers prior approval for entry to the US. It is currently free to obtain, and lasts for two years. People who already have a valid form will not have to pay until their current one expires.
Martin Lewis, creator of MoneySavingExpert.com, has urged anyone even considering a trip to the US to apply for a form now in order to avoid the charge.
He said: "The security authorisation lasts for two years, so do it now and it'll be free if you travel in that time. Yet leave it for a month and you'll have to pay for it.
He added: "It is rather strange that this fee is mainly going to promote US tourism. You would have thought keeping it cheaper to get in would help more - after all, it's free for most Americans to come here."
The Esta scheme was introduced in January 2009 but made mandatory from January 2010.
It applies to 35 countries with US "visa waiver" status, and replaced the green I-94 card which passengers used to fill in on their flight to the US.
An estimated four million Britons visit the US each year.