You should apply for visa as soon as possible, and no later than 60 days before the travel date. If the conference is scientific in nature, or the applicant has a scientific background, the visa application should be made no later than 90 days in advance of the travel. Wait timings vary by the consulates and some consulates may require more time. Additional delays may be caused by security clearances or administrative processing that may be needed after the interview in some cases.

Certain large and established Indian companies that send lot of employees on business visas may qualify for Business Executive Program.

Some consulates call it urgent appointment or emergency appointment as well.

Some consulates have the procedures to schedule an expedited appointment. However, it is discretionary and depends on the several factors such as the urgency of the travel and the US national interests involved.

• Clearly indicate the date of travel on the application and provide contact information such as local phone number of the applicant.
  
  
• Clearly explain why it is important (i.e., explain what is at stake) to expedite the appointment.
  
  

US embassy/consulate will review such requests and grant expedited interview appointments within the constraints of their workload.