1. The sponsoring partner must be a U.S. Citizen.
2. Both parties must be unmarried and eligible to get married in the US.
3. The parties must have met, in person, face-to-face within the 2 years prior to filing the case. This requirement is strictly enforced by USCIS so make sure you have concrete proof.
There are 2 exceptions (waivers) to this rule –
a) Meeting the Fiance in person would violate strict and long-establish cultural customs or social practice. This exception would apply if the culture/religion prohibits ANY type of face-to-face meeting, even if there is a chaperone.
The second exception is
b) Extreme Hardship to travel. This comes down to an impossibility to travel, for example a medical condition. It is exceedingly difficult to get the waiver, so you need to make sure that you have a valid reason with lots of documents proving the custom or hardship.