The K-1 visa is for the foreign fiancé of a U.S. citizen to enter the United States to marry his/her fiancé. Once you enter the U.S. on a K-1 visa, you have 90 days to marry a U.S. citizen. A K-1 visa does not allow foreign nationals to stay in the United States for more than 90 days and can’t be extended. But once married, the foreign national may stay in the United States if he or she applies for adjustment of status through a K-1 visa entry.