British travellers are to be fingerprinted on arrival in the US
UK officials have said they are working with their American counterparts to try to save thousands of British visitors having to buy visas to enter the US.
Currently British travellers can visit the US for up to three months without a visa under the "visa waiver programme".
But from 26 October citizens of all 27 visa waiver countries must have new "biometric" passports containing digital photographs and fingerprints.
And the UK authorities will not be able to issue them before the deadline.
So all British travellers issued passports after 26 October will have to buy visas from the American Embassy before travelling and have their fingerprints and photographs taken on arrival in the US.
British officials are believed to be lobbying Washington hard to extend the deadline or make alternative arrangements.
Correspondents say that most other visa waiver countries - mainly in western Europe, but also including Japan and Australia - will also be unable to issue "biometric" passports before the US deadline.
A British Embassy spokesman said: "We are in close contact with the Department of Homeland Security on the issue of biometrics, and have been from the start, and we continue to work to find a solution."
Homeland security secretary Tom Ridge said the US aimed to be "open to visitors but closed to terrorists".
About 15.1 million tourists entered the US under the visa waiver programme last year, accounting for two-thirds of spending by foreign visitors.
Holidaymakers heading for winter sunshine breaks in Florida and ski resorts for the early season are likely to be among the first of many queuing for visas at the American Embassy in Grosvenor Square, London.
On Monday, stringent new security regulations were introduced at the US's 115 international airports and 14 major seaports,
The system allows officials to instantly check an immigrant or visitor's criminal background.
Since 11 September 2001, flying anywhere has changed. Two of the hijackers on that day had entered the US on student visas, but neither ever turned up for college.
The Department of Homeland Security believes the extra immigration checks would have picked up on that discrepancy.
For the American Government there can never be too many checks. Air travel may now be more complex but the US administration is adamant it will not deter visitors from heading to the US.
Instead, they believe the very public extra security is a reassurance - an obvious sign that America is looking hard for those who threaten its citizens.
Shit shit shit shit shit shit shit.
And I won't be allowed to queue for the loo on a plane anymore either.