本人婚姻绿卡，老公收入太低，无法为我作经济担保。我的一位老美朋友同意为我作担保，当她看到担保人的责任，即为被担保人提供资金支持直到被担保人成为美国公民或者得到40个工作季节（相当于10年）。就有点犹豫了，感觉责任太大。
我想问问，如果AP下来，我找到工作，并且报税，那时，我的老美朋友可以撤销经济担保吗？
-As far as I understand, a person CAN withdraw the affidavit of support any time until the green card is issued. Once the green card is issued, you can not withdraw the 经济担保 (affidavit of support).
There are regulations effective as of June, 2006, that state that, in the event of an ADJUSTMENT OF STATUS case, a sponsor (substitute, joint, etc) or anyone, really, who has presented a signed Form I-864, the sponsor MAY DISAVOW HIS OR HER AGREEMENT TO ACT AS SPONSOR only if he or she does so IN WRITING and submits the document to the immigration officer or immigration judge BEFORE the decision on the adjustment application.
The authority is found in the FEDERAL REGISTER, Vol. 71, No. 119, Wednesday, June 21, 2006, page 35755
The link is here: http://bulk.resource.org/gpo.gov/register/2006/2006_35755.pdf
