An alien who is a beneficiary of a permanent resident petition filed by a U.S. citizen spouse within two years after the marriage is granted conditional permanent resident status valid for two years.
Before the second anniversary date of the issuance of the conditional residence, the US citizen and the alien spouse need to file a joint petition to remove the conditional residence and convert the status to full permanent residence. If the US citizen spouse refuses to sign the joint petition, the alien spouse may not obtain full permanent residence unless the INS waive the requirement under limited circumstances.
There are three grounds for the waiver of the joint petition: extreme hardship, good faith marriage and battered spouse or child.