The US government is to start charging UK travellers $14 (£9) to apply for permission to enter the country.
The compulsory Electronic System for Travel Authorisation (Esta) is free at present, but from 9 September visitors to the US will have to pay for it.
It lasts for two years; people who already have a valid form will not have to pay until their current one expires.
The scheme was introduced in January 2009 but was made mandatory from January 2010.
It applies to all 35 countries with US "visa waiver" status.
BBC News - US to charge £9 for Esta compulsory travel entry form