The K-3 Visa is a non-immigrant (temporary visiting) visa for a spouse of a U.S. citizen to come to the US, while his/her permanent stay case is still pending. The K-3 visa must be filed and the visa must be issued in the country where the marriage took place. After the visa process has been completed, and the visa is issued, the spouse can travel to the United States to wait for the processing of the immigrant visa case.
The Legal Immigration Family Equity Act and its amendments (LIFE Act) established a new nonimmigrant category within the immigration law that allows the spouse or child of a U.S. citizen to be admitted to the United States in a non-immigrant category. The admission allows the spouse or child to complete processing for permanent residence while in the United States. It also allows those admitted in the new category to have permission for employment while they await the processing of their case to permanent resident status.
A K-4 visa is a version of the K-3 visa but for unmarried children under the age of 21. Before a K-4 visa can be issued to a child, the parent must have a K-3 visa or be in K-3 status.