U.S. presidential contender Barack Obama pledged Wednesday his "unshakable commitment to Israel's security" during a visit to the rocket-scarred town of Sderot, emphasizing his support of the Jewish state's right to defend itself. - "The state of Israel faces determined enemies who seek its destruction, but it also has a friend and ally in the United States that will always stand by the people of Israel," Obama told reporters in Sderot, a southern city subjected to daily rocket barrages fired by Palestinian militants from the Gaza Strip before a fragile truce between Israel and Hamas last month curbed the attacks. - He also said a nuclear Iran would pose a "grave threat," and vowed to use "big sticks and big carrots" to persuade the country's leaders not to develop nuclear weapons. - Earlier in the day, Obama vowed to maintain a "special relationship" with Israel as president after meetings in Jerusalem as part of his weeklong Mideast tour, which also...