Democratic presidential candidate Barack Obama declared Monday that the world must press Iran through sanctions and diplomacy to stop its nuclear program, so that Israel does not feel its "back is against the wall" and that it therefore has no choice but to attack. Speaking at a campaign event in Iowa, Obama said that a nuclear-armed Iran would be a "game-changer for the region." Obama stressed that Israel, "one of our strongest allies in the world," would feel hugely threatened given claims by Iran's President Mahmoud Ahmadinejad that he would wipe it off the world map. In response to a question from a crowd of about 250 supporters, he said: "My job as president would be to try to make sure that we are tightening the screws diplomatically on Iran, that we've mobilized the world community to go after Iran's program in a serious way and to get sanctions in place so that Iran starts making a difficult calculation. "We've got to do that before Israel feels like its back is to the wall," he reiterated when asked if Israel felt that it had free reign to take action against Iran if the West did not convince Teheran to curb its nuclear ambitions. "I don't want to speculate on whether or not Israel feels like it has a green light or not," he said. "What is not speculation is that we have to act much more forcefully and effectively on the world stage to contain Iran's nuclear capabilities." Defense Minister Ehud Barak said Wednesday that US President George W. Bush's administration remained opposed to any military strike against Iranian nuclear facilities. "Our position is that no option is to be taken off the table, but in the meantime we have to make diplomatic progress," Barak told Army Radio. In a meeting with US Secretary of State Condoleezza Rice at his residence in Tel Aviv on Monday night, the two discussed Iran. According to a statement that his office put out after the meeting, Barak said that Israel was carefully watching Iran's efforts to develop nuclear arms. After calling on the US to continue its push for effective sanctions against Iran, Barak emphasized Israel would not tolerate a nuclear Iran, and is not "taking any option off the table." Barak also raised with Rice the continued rearmament of Hizbullah, and also discussed Syria's recent attempts to upgrade its arsenal with state of the art Russian weapons. Obama said in Iowa that after visiting Israel last month, he believed Israel's "general attitude is we will not allow Iran to get a nuclear weapon." "They recognize there are no good military options but they also recognize that from their perspective it is unacceptable to allow Iran to have a nuclear weapon," he added.