Travellers to the United States must have either a valid visa, or must complete the ESTA (Electronic System for Travel Authorization) form if they are citizens of Visa Waiver Program (VWP) countries.
VWP travellers are required to complete the ESTA form online and pay the $14 fee no later than three days in advance of their journey.
The ESTA provides advance authorization to travel to the United States for tourism or business for stays of 90 days or less without obtaining a visa.
Countries currently enrolled in the Visa Waiver Program include: Andorra, Australia, Austria, Belgium, Brunei, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Japan, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Monaco, Netherlands, New Zealand, Norway, Portugal, San Marino, Singapore, Slovakia, Slovenia, South Korea , Spain, Sweden, Switzerland, Taiwan, United Kingdom.
If you are not a citizen of a VWP country, please visit usembassy.gov for information on required visas for your country.