But Republican Sen. Lamar Alexander of Tennessee says President Barack Obama is doing the right thing by trying to win international backing for more penalties. Alexander calls Iran the "most dangerous enemy" the United States faces.
Sen. Joe Lieberman, the Connecticut independent, says a nuclear-armed Iran would, in his words, "change the world," and he called for tougher, faster sanctions from Congress.
Iran rejects calls to abandon its nuclear program, arguing that it is for peaceful purposes and not for developing weapons.
Alexander and Lieberman spoke on "Fox News Sunday."
