JERUSALEM, July 23 (Xinhua) -- Visiting U.S. Democratic presidential candidate Barack Obama reiterated Wednesday that Iran should be prevented from obtaining nuclear weapons, saying a nuclear Iran would be a game changer.

"A nuclear Iran would be a game-changing situation, not just in the Middle East, but around the world," Obama told reporters at a press conference in the rockets-stricken town of Sderot in southern Israel.

U.S. Democratic presidential candidate Senator Barack Obama pauses during a ceremony in Janusz Korczak Square at Yad Vashem Holocaust Museum in Jerusalem, July 23, 2008. (Xinhua/Reuters Photo)

"A nuclear Iran would pose a grave threat, and the world must prevent Iran from obtaining a nuclear weapon," stressed the U.S. senator, adding that he would "take no options off the table" in order to achieve that goal.

 Asked about his previously stated notion of having talks with Iranian leaders, Obama said "we should exhaust every possible avenue" on Iran, dealing with the issue with "carrots and sticks."

Israel's President Shimon Peres (R) and U.S. Democratic presidential candidate Barack Obama deliver joint statements to the media in Jerusalem July 23, 2008. (Xinhua/Reuters Photo)

If Iran rejects the offers, explained the U.S. presidential hopeful, then "we will be in a stronger position" to call on the international community to respond collectively against the Islamic republic.

Israel, the United States and some other countries accuse Iran of secretly developing nuclear weapons, but Iran denies the charge, insisting that its nuclear program is only for civil purposes.

Accompanied by Israeli Foreign Minister Tzipi Livni and Defense Minister Ehud Barak, Obama also repeated his "unshakable commitment to Israel's security" and urged the Jewish state and its Palestinian neighbor to achieve true, lasting peace.

The candidate, who arrived here late Tuesday as part of a week-long overseas tour, is to meet with Israeli Prime Minister Ehud Olmert later Wednesday, following a series of talks with Israeli and Palestinian officials, before he heads for Europe early Thursday.