Agents and operators are being urged to sign up clients for the US’s Electronic System for Travel Authorisation (Esta) before September 8 when a $14 charge will be introduced.

Charles Bartoldus, the US Department of Homeland Security’s attaché to the UK, said consumers could now apply for an Esta, which lasts for two years, even if they do not have an immediate trip on the horizon.

Robert Neumann, programme manager for the US Customs and Border Protection, added: “We’re suggesting consumers do it now – we don’t want them all going on there on September 7.”

To date, 23 million travellers globally have filled out an Esta form since its launch two years ago, 26% of whom are UK citizens.

“Compliance has been very good, we’re very happy with the number of travellers going on the website and filling the form out,” Neumann added.

Bartoldus said Esta had also proved popular with airlines, many of which have included links on their own sites to the online form.

Some travel agents are receiving a commission for filling out the forms on behalf of their customers, although Bartoldus warned agents doing this that they must be as truthful as possible.

“The reality is, if someone forgets something the person filling the form out is only liable for the information they were given; if the person didn’t tell you then you weren’t told,” he said.

“If they told you they were arrested for drunken conduct in Philadelphia, and the agent said don’t worry about it, then the agent would be held liable.”

Bartoldus said it was thought unlikely the new charge would deter travellers from visiting the country. However, he added that the charge, which sees $10 donated to a fund set up to market the country and $4 pay for administration costs, could be reviewed if it led to a significant drop in visitor numbers.

Kate Burgess-Craddy, chairman of Visit USA, said she thought the charge was unlikely to cause problems.

“It has been amazing how much agents have got on with it. We’ve not had any feedback that it has gone wrong,” she said.