A bigger issue is whether your application for adjustment of status will be reviewed for preconceived intent since you entered the US on a visa waiver. However, the short answer to your question is you use form I-864. The Affidavit of Support (I-864) is a legal contract between you (the petitioner for an immigrant visa applicant) and the US Government. It ensures that the visa applicant has adequate means of financial support and is unlikely to become a public charge after entering the US.
Adjustment of status (AOS) decisions are discretionary, not mandatory and officers can deny AOS because the application was submitted too quickly.
If a person enters the United States in certain nonimmigrant (temporary) visa categories with the obvious intention of applying for immigrant (permanent) status, their adjustment of status (AOS) application can be denied by the USCIS in the exercise of discretion. The nonimmigrant visa categories that can never intend to acquire permanent status are B-1/B-2 Visitors, F-1 Students, J-1 Exchange Visitors, Q Cultural Exchange Visitors, TN Visitors or Visa Waiver Visitors. Applicants for AOS must not only prove to the USCIS that they have been "in status" at all times that they have been in the United States, but also that they have not acted in bad faith for their latest entry. The USCIS has adopted the "30/60 Rule” used by the Dept. of State’s Foreign Affairs Manual (9 FAM 40.63 n4) when examining events that occur shortly after entry.
IMMEDIATE RELATIVES ARE TREATED DIFFERENTLY: If the AOS application was filed more than 60 days after entry, the presumption is that the applicant acted in good faith. With regard to immediate relatives, preconceived intent is not supposed to be presumed and is not supposed to be the basis for an AOS denial if it is the only adverse factor (Matter of Cavazos, 17 I&N Dec. 215 (BIA 1980), Matter of Ibrahim, 18 I&N Dec. 55 (BIA 1981)) Matter of Battista, 19 I&N Dec. 484 (BIA 1987)). Keep in mind that the USCIS still reserves the right to investigate any AOS case if there is evidence of wrongdoing. If an AOS applicant has anything in his or her past visa history that suggests that he or she may have abused the visa process, or otherwise tried to take shortcuts, the USCIS has made it clear that they can deny such AOS applications in the exercise of discretion.
Steven N. Garmo
2010 Michigan Super Lawyer