There are several restrictions on visitors to the United States, depending on the nationality of the visitor and the place from which you leave to arrive in the U.S.
VISASUnless you are a citzen of a country listed under the "Visa Waiver" countries (below) or of Canada, you will need a visa to enter the United States.
VISA WAIVER COUNTRIES
Andorra Iceland Norway Australia Ireland Portugal Austria Italy San Marino Belgium Japan Singapore Brunei Latvia Slovakia Czech Republic Liechtenstein Slovenia Denmark Lithuania South Korea Estonia Luxemburg Spain Finland Malta Sweden France Monaco Switzerland Germany The Netherlands United Kingdom Hungary New Zealand
Citizens of countries participating in the Visa Waiver Program do not need to apply for visas to attend the Conference. You may enter the United States using just your passports and your Conference Registration Notice. At the port of entry into the U.S, please request to be given a "Visa Waiver for Business" (WB) status. That will allow you to stay in the U.S. for the length of the Conference. Official letters of invitation (without financial commitment) to help overcome administrative difficulties in some countries can be sent upon written request to the conference administrator.
IMPORTANT: Effective January 12, 2009, all Visa Waiver travelers will be required to obtain an authorization via ESTA before traveling to the United States: https://esta.cbp.dhs.gov/
NON-VISA WAIVER COUNTRIES
Citizens of countries not participating in the Visa Waiver Program will need to request a Business (B-1) visa at the nearest U.S. Consulate. Please present at the Consulate your Conference Registration Notice, along with your valid passport. We urge you to do this EARLY, as there are often delays in this process. Official letters of invitation (without financial commitment) to help overcome administrative difficulties in some countries can be sent upon written request to the conference administrator.
Although Canada is not a Visa Waiver country, Canadian citizens do not need to apply for visas at the U.S. Consulate. Citizens of Canada may enter the country using just their passports, along with their Conference Registration Notice. Please request at the port of entry status as a Visitor for Business (B-1).