Home Minister Azmi Khalid said this did not mean the crackdown would not go ahead, but that the migrants would be given one last chance to leave first.
He said the decision had been made on the request of tsunami-hit Indonesia, where most of the migrants are from.
Malaysia has blamed illegal migrants for rising crime in the country.
Some 380,000 migrants left Malaysia ahead of the latest deadline to avoid punishment, but at least 400,000 are believed to remain.
