CIA agents or any individual government official cannot grant American citizenship. Acquiring citizenship, by birth or naturalization, is strictly governed by the United States Code and is a lengthy process.
Marrying a U.S. citizen does not automatically make a non-resident alien a citizen, otherwise that would be an easy loophole around immigration laws. The person in question must first apply for and be granted a Permanent Resident Card (green card) and reside in the country for at least three years, they must also submit to an interview to determine if they are actually a couple or are just faking it to become a citizen. As shown here they must answer questions about one another, things like when did they meet, when did they get married, when is their spouse's birthday, names of family members and important life events.