A bipartisan deal on immigration legislation would need tough enforcement and even stricter penalties for those who came to the United States illegally, a leading Republican at the center of negotiations said Sunday.

Senator Marco Rubio, who’s among the eight senators writing a plan that’s expected to come out today, tried to promote and defend the framework for the emerging overhaul that would provide a path toward citizenship for those who came to the country illegally or overstayed their visit.