Fiancee (K-1) visa is an non-immigrant visa allowing your Fiancee to enter the United States for the purpose of marriage. The marriage must take place within 90 days of your fiancee entering the United States.
If the marriage does not take place within 90 days or your fiancee marries someone other than you (the U.S. citizen filing USCIS Form I-129F – Petition for Alien Fiancee, your fiancee will be required to leave the United States. Until the marriage takes place, your fiancee is considered a nonimmigrant. A nonimmigrant is a foreign national seeking to temporarily enter the United States for a specific purpose.
A fiancee may not obtain an extension of the 90-day original nonimmigrant admission.
You are required to submit your Petition for Alien Fiancee (Form I-129F) according to your place of residence. There are four main Service Centers in the United States, which handle I-129F application packages. Those applications should be mailed to USCIS Service Centers.
Please note: Your fiancee may enter the United States only one time with a fiancee visa. If your fiancee leaves the country before you are married, your fiance(e) may not be allowed back into the United States without a new visa.