BOSTON - Newly elected Gov. Deval Patrick said Thursday he is rescinding a month-old policy imposed by his predecessor that allowed state troopers to arrest illegal immigrants. The Democrat said he is replacing it with a program to deport convicted criminals serving time in state prisons. Patrick said the shift would free troopers to focus on gun, gang and drug crimes, while removing illegal immigrants after they complete their sentences. "I think that strikes the right balance between our responsibility to assure public safety and our responsibility to respond to the concerns about illegal immigration," he said. Former Gov. Mitt Romney, who is considering a bid for the Republican presidential nomination, announced just before leaving office that the state would allow state troopers to enforce federal immigration laws. No one had been arrested under the program, the result of an agreement with the U.S. Immigration and Customs Enforcement agency, since the troopers had not completed their training. Under the new initiative, a dozen Correction Department employees will review the status of convicts and consider them for deportation. Public Safety Secretary Kevin Burke said the State Police worried that their expanded duties would take time away from their central law enforcement duties and compromise troopers' ability to gather intelligence and solve crimes in immigrant communities. Burke estimated there are 700 illegal immigrants in state custody. Patrick said if prisoners are determined to be illegal immigrants, "they're out of here" after they complete their sentence. ICE has signed similar agreements with correction officials in California, Florida and Arizona.