If a marriage has lasted less than 2 years when the green card application was approved, the alien spouse would have been given conditional residency. Within 90 days before the expiration of conditional residency, the spouses are to file a joint petition to remove conditions. In some circumstances, the alien spouse may file the petition to remove conditions by himself. However, filing by himself requires a higher level of proof.
From the information in your post, your marriage was likely less than 2 years when the green card was approved.
Failure to timely file the petition to remove conditions results in an automatic revocation of the alien spouse's legal residency.
Even if your spouse received unconditional permanent residency, you remain liable for his financial support as agreed in the I-864 until one the conditions specified there comes true.
If you two pretent to still be living together as a husband and wife so that his immigration applications may be approved, both of you may end up being charged criminally. For the alien spouse, there is no statute of limitation for the government to revoke immigration benefits obtained fraudulently. That is, for example, 30 years from now, the government can still come back and take away his citizenship (if he has it then) and permanent residency if the government can prove fraud.
You may want to review your facts and options with an attorney.
Does he have a temporary green card or apermanent green card. If it is a permanent green card you do not have to sign anything. However, you are still responsible under the affidavit of support.
Nikki Mehrpoo Jacobson
Under Section 216 of the Immigration and Nationality Act, it appears that your husband was approved for conditional residence to the United States. In order for him to file for the removal of conditional residency he has to prove that he has married you in good faith. It appears that your husband wants you to sign the form I-751 and therefore he is trying to contact you. Remember, he can also apply for the I-751 without a divorce from you provided that he can prove that he has been a victim of cruelty.
Naresh M. Gehi, Esq