(ABC News)

During an interview for "This Week," Defense Secretary Leon Panetta assured me that the United States has readied plans to carry out a military strike on Iran to prevent the regime from obtaining nuclear weapons if diplomacy fails to dissuade the country from its current path.

"One of the things that we do at the Defense Department, Jake, is plan.  And we have - we have plans to be able to implement any contingency we have to in order to defend ourselves," Panetta said.

The secretary of defense was responding to my question about recent comments made by American ambassador to Israel Daniel Shapiro - and reported by ABC News' Alexander Marquardt - that the United States has already made preparations for a potential strike on Iran. The United States, joined by five other countries, is currently engaged with Iran in negotiations over its nuclear program.

"It would be preferable to solve this diplomatically and through the use of pressure, than to use military force," said Shapiro. "But that doesn't mean that option isn't fully available. Not just available, it's ready. The necessary planning has been done to ensure that it's ready," he said.

During our interview, Panetta expressed hope that the nuclear standoff with Iran could be solved peacefully, but left no doubt as to the position of the United States: An Iran with nuclear weapons is not on the table.

"The fundamental premise is that neither the United States or the international community is going to allow Iran to develop a nuclear weapon.  We will do everything we can to prevent them from developing a weapon," he said.