Adm. Mike Mullen, the top-ranking U.S. military officer, said a military strike would have severe downsides -- but so would a nuclear-armed Iran. He described the challenge as a choice between two very bad options.
"I am extremely concerned about both of those outcomes," he said.
But Mullen, speaking on NBC's "Meet the Press," said the military option is an important one. He said it's a decision that's up to the president to make.
"The military options have been on the table and remain on the table," he said. "It's one of the options that the president has. ... I hope we don't get to that, but it's an important option and it's one that's well understood."
Asked whether the U.S. military has an attack plan, Mullen said: "We do." He did not elaborate.
Mullen, who addressed the topic in the wake of new sanctions against Iran being imposed by the United States, European Union and United Nations, said there is a narrow space between those two options. He said that space involves sanctions, diplomacy and international pressure and that he remains "hopeful" the combination will yield positive results.
"It's those unintended consequences that are difficult to predict in what is an incredibly unstable part of the world," Mullen said.