You will need a B1 visa or a business visitor visa to participate in international conferences in the USA. Invitation Letter: An official letter from the conference organizers is critical.Yes, the organizers of the conference can send a letter to the US embassy or consulate to request a visa for you. We created three free templates you can use as a starting point. After reading this instruction page, you will be entitled to fill out your information, agree to our terms and conditions, then submit the application form. Send an email to us requesting that we mail you a copy of your invitation letter. Make your VISA appointment as soon as possible if you intend to attend CROI 2025, as some countries require up to a year to process visa applications. Please note that Texas Global does not write letters of invitation. It should come directly from you. To obtain a visa invitation letter for Display Week 2025, please fill out the form below.