Pat Buchanan, a leading conservative and former candidate for the Republican presidential nomination, told NBC's "Meet the Press" the bill before the U.S. Senate is "amnesty, pure and simple."
"We've got 12 (million) to 20 million illegal aliens in this country, massive criminality being rewarded with blanket amnesty and put on a path to citizenship," said Buchanan.
However, Rep. Louis Gutierrez, D-Ill., chairman of the congressional Hispanic Caucus Immigration Task Force, said the measure is not amnesty, but is "the pathway to legalization."
"We have an immigration system that is broken," he said, "that's a nightmare."
President George W. Bush has failed to enforce the U.S. borders, Buchanan said.
"The Constitution of the United States obligates the president to defend the states from an invasion. The president himself says in his first five years, 6 million people tried to break into this country," said Buchanan. "This is not immigration ... this is an invasion of this country."
"The same argument that Pat makes today are the arguments that have been made in the past -- they were wrong then, they are wrong today," said Gutierrez.