Travellers from 27 countries, including Britain, will be required to register online with US authorities at least three days before leaving to visit America, it will be announced today.

This latest measure aimed at bolstering American security is expected to take effect from January 2009.

Last year, European companies expressed concern when the US homeland security department floated proposals to make passengers register with US authorities 48 hours before travel. Critics feared this could complicate last-minute business arrangements.

The introduction of the new 72-hour notice period will be announced by the homeland security secretary, Michael Chertoff, later today, according to a US government official.

The rules will apply to citizens from the 27 nations of the visa waiver scheme. This includes most of western Europe as well as Australia, Brunei, Japan, New Zealand and Singapore.

Although the measure will require registration 72 hours before travelling, successful applications will be valid for multiple entries over two years.

Passengers will be able to register in advance from August this year through travel agents, airline websites or a special US government website.