Democratic candidate Obama promised to examine every option, "including military, to prevent them from obtaining a nuclear weapon," while his Republican rival McCain spoke about the possibility of a preemptive war against Iran.
He went on to criticize the Bush administration for wasting eight years instead of handling the Iranian issues.
"I do think that it is important for us to use all the arrows in our quiver. And we have not applied the kind of tough diplomacy over the last eight years that I think could have made a difference," he said.
McCain was asked if his administration's policy would be to engage in preemptive war against a country that might pose a threat to the US but that hasn't attacked it. He responded that he would command a preemptive attack "if it's a provable direct threat, bringing Iran as an example.
"Suppose that the Iranians had nuclear weapons. And you had a whole lot of other information about Iranian intentions and you could make the case to the American people and to the world, I think it's obvious that we would have to prevent what we're absolutely certain is a direct threat to the lives of the American people," he said.
Headed for debate
The two separate interviews were held before last weekend and both focused on the economic crisis in Wall Street. The first debate between the two candidates will be held on Friday in Mississippi and will deal with defense and foreign affairs.
Two additional debates will be held on October 7 and October 14.
McCain, who has served in the American Congress for 26 years, enjoys an advantage over Obama in terms of his experience in international issues. The Democratic candidate hopes to take advantage of the television debate in order to change the public opinion on this issue, and plans to spend the next three days preparing for the debate.
Obama's associates have noted that he is an excellent speaker, but does not excel in television debates. He is expected to rehearse the debate with his team of experts in the next three days, with Greg Craig, one of former President Bill Clinton's defense attorneys in the Monica Lewinsky affair, playing McCain.