An Affidavit of Support is not required during the initial K-1 visa application process. However, the U.S. citizen petitioner must submit Form I-134, Declaration of Financial Support, during the visa interview stage to demonstrate that they have adequate financial means to support their non-citizen fiancé(e) in the United States.
This form promises that the U.S. citizen petitioner will financially support their fiancé(e) so they will not become a public charge.
When the non-citizen fiancé(e) applies for adjustment of status to become a permanent resident after marriage, the U.S. citizen spouse must submit Form I-864, Affidavit of Support. This form is legally binding and guarantees that the U.S. citizen spouse will provide financial support for their spouse to ensure they do not rely on public assistance.