Letters of invitation

We’re excited to welcome our international visitors! Please note that all travelers must have a valid U.S. travel authorization before arriving in California. The type of authorization you need depends on the purpose and length of your visit.

If you plan to stay for fewer than 90 days and are a citizen of one of the countries participating in the U.S. Visa Waiver Program, you do not need a visa. Instead, you can apply for an Electronic System for Travel Authorization (ESTA) online.

Travelers who are citizens of African or South American countries are not eligible to travel to the United States using an ESTA and will need to apply for a B-1 visa. We recommend starting this process as early as possible, as visa processing times can take several weeks or longer.

If you have any questions or need help with the process, your nearest U.S. embassy or consulate will be happy to assist you.

International visitors are encouraged to start their visa application process early. Upon request, we will be able to issue visa letters of attendance as soon as registration has been received. 

Please email Melissab@ASAS.org to request your letter. You will need to include the following information:
Full Name
Institution
Address
Country
Passport number
Date of Birth
Nationality