Voters in the big northeastern state of Pennsylvania are casting ballots on Tuesday in a crucial Democratic presidential primary that most analysts say Senator Hillary Clinton must win to stay in the race.
Senator Clinton and her rival, Senator Barack Obama, appeared on U.S. television news shows Tuesday, making last-minute appeals to Pennsylvania Democrats.
On foreign policy, Clinton delivered on ABC's Good Morning America her toughest stance yet on Iran, saying the United States would "totally obliterate" Iran if Tehran launched a nuclear attack on Israel while she is president.
She also said on NBC's Today Show a victory in Pennsylvania, along with her wins in California and New York, will prove that Obama cannot win in states with large numbers of delegates.
Senator Obama said on ABC's Good Morning America he would respond forcefully to an Iranian attack on Israel, but dismissed Clinton's use of words such as "obliterate" as ineffective "sabre rattling".
He also said on NBC's Today Show that although he does not expect to win in Pennsylvania, he had successfully cut into his rival's lead there.