From October 1st, travellers entering the United States under the Visa Waiver Programme must have a machine-readable passport, according to the US State Department.
"Any traveller without a machine-readable passport will be required to obtain a visa before coming to the United States" from that date, the State Department warned yesterday.
Ireland is one of 27 countries whose citizens are entitled under the programme to enter the US for general business or tourist purposes for a maximum of 90 days without needing a visa.
In effect this means that a traveller with a hand-written passport - not readable by scanning machines - may be denied entry by US immigration officers unless it contains a non-immigrant visa, which costs $100 worldwide.
The Passport Office in Dublin has been issuing machine-readable passports for the last 10 years and the London embassy is also equipped to issue machine-readable passports.
However, people who obtained passports in most other Irish embassies or consulates abroad - such as expatriates, or visitors renewing or replacing lost or stolen passports - will likely be in possession of hand-written passports.
Irish embassies now send passport and renewal applications to Dublin if a machine-readable passport is required.
Machine-readable passports enhance security as they can be scanned at entry and exit points to verify the integrity of the passport data, the State Department said.
They contain two typeface lines printed at the bottom of the biographical page that can be read by machine.
The new regulation is mandated by the USA Patriot Act of 2001, passed shortly after the attacks on September 11th, 2001. It applies to adults and children.
The countries in the Visa Waiver Programme are: Andorra, Australia, Austria, Belgium, Brunei, Denmark, Finland, France, Germany, Iceland, Ireland, Italy, Japan, Liechtenstein, Luxembourg, Monaco, Netherlands, New Zealand, Norway, Portugal, San Marino, Singapore, Slovenia, Spain, Sweden, Switzerland and the United Kingdom.
The Irish consulate in New York said Irish citizens and those who hold a US visa, green card or other document allowing them to reside in or enter the US are not affected by this change.
"The Embassy of Ireland in Washington and the Consulates General of Ireland in New York, Boston, Chicago and San Francisco currently issue non-machine-readable passports," the consulate said.