As of Monday, travellers to the United States by air or sea who do not require a visa must register online to receive authorisation before buying tickets.
Switzerland is one of 35 countries whose citizens are not required to obtain visas for US entry. An estimated 270,000 Swiss travel to the US every year.
The online security screening system adds to existing identity and travel checks that the US has imposed on foreigners since the September 11 attacks.
The "Electronic System for Travel Authorization" (ESTA), which went online in August 2008, is now mandatory for all visa-free visitors to the US from January 12.
ESTA collects the same information as the I-94W green form that travellers from visa-free countries filled in on the plane and handed to border control on arrival in the US.
The scheme will not apply to land border crossings into the US, where authorities will continue to use the paper forms.
ESTA applications are made in four steps on the Department of Homeland Security's website.
On the online form, the traveller must give his name and travel information and state whether he has a communicable disease, is a drug abuser, has already been denied a US visa or "is seeking entry to engage in criminal or immoral activities".
The US authorities ask visitors to register as early as possible as it may take up to 72 hours to process an application, which is valid for two years. But in most cases a reply is sent within almost a minute, according to the US embassy in Bern.
Around five per cent of cases are turned down. In this happens, the new online system has its advantages as the traveller doesn't make the journey for nothing, says the embassy.
If the ESTA application is refused, an applicant still wishing to travel to the US will need to apply for a visa. But this time he will have to pay – unlike ESTA, which remains free for now.
But the 72-hour period may prove to be problematic, especially for a trip at short notice.
"Last-minute journeys are rarely made to the US and normally bookings are made some three weeks before travelling," said Prisca Huguenin-Lenoir from M-Travel Switzerland.
The new electronic system is the latest in an overhaul of US travel regulations since the September 11 attacks. Visitors already have to provide fingerprints to US border guards when entering the country; airlines use forwarded data including passenger names, addresses, seat numbers, credit card information and travel details.
The US embassy says the traveller-screening process will be simplified thanks to online registration.
But does online screening necessarily mean greater data protection? In the past the Federal Data Protection and Information Commissioner has expressed scepticism about the safety of online forms.
"As to the specific case of the ESTA forms, it was not consulted but informed by the US," said spokeswoman Eliane Schmid.
The US Department of the Interior says it plans to keep ESTA data for a year after the authorisation expires. Data will then be archived for 12 years for possible national security or justice requirements.
The travel industry has already warned its customers about the introduction of the new form.
"By examining things closely, in the medium to long term this system will be a simpler one," said Huguenin-Lenoir.
"For the traveller, the entry formalities for the United States will be quicker as the form will already be in the hands of the customs authorities."
And technophobes still have the possibility of filling out the online form directly at their travel agents. This is usually free if a reservation is made.
swissinfo, Pierre-François Besson
Visa or no visa
If Swiss citizens are travelling for up to 90 days and carry an eligible passport, they can visit the US without a visa under the country's Visa Waiver Programme.
However, they still have to fill out the online travel authorisation form, ESTA, on the US Homeland Security Department website, including forms for accompanying children.
To travel to the US without a visa, Swiss passport holders require a model 03 passport, if issued before October 26, 2006, or a 06 passport model (biometric passport).
However, passport models 85 and 03 issued after October 26, 2006 are not valid for travel to the US without a visa.
Travellers who obtain a visa are not required to register via ESTA but have to be interviewed at a US consul or embassy and pay for the visa.