An affidavit of support is a document an individual signs to accept financial responsibility for another person, usually a relative, who is coming to the United States to live permanently. The person who signs the affidavit of support becomes the sponsor of the relative (or other individual) coming to live in the United States. The sponsor is usually the petitioner of an immigrant petition for a family member.
The reality is that, ordinarily, one cannot actually be sponsored for a standard B-1/B-2 visa; but, it is possible for a person in the U.S. to provide financial sponsorship through the submission of a signed affidavit of support, using form I-134. For many applicants, however, submitting this form could actually do more harm than good.」 以及：「Avoid Submission of Form I-134 unless Specifically Requested.
我为岳父母申请延期的时候，他们没有提供任何经济证明（因为他们的材料都在中国），我在申请信中明确表示会负担他们的开销（参见这里），并且附上了我的 Bank Statements，没有填写 I-134，结果顺利批准。 B1/B2 签证延期的教程参见这里。