Speaking to CBS News in Jerusalem, Romney said he still favored diplomatic and political pressure on Tehran and stressed that not all diplomatic steps had been taken.
"We should use every diplomatic and political vehicle that's available to us to keep Iran from becoming a nuclear capability state," Romney said in an interviewed aired on CBS' "Face the Nation."
"Those actions should be executed with the greatest speed that we can muster," Romney continued. "If all those options fail -- and they've not all been executed; they've not all failed entirely at this stage -- then we do have other options, and we don't take those other options off the table."
Romney's remarks came in the wake of statements from a senior national security adviser to his campaign that a Romney administration "would respect that decision" if Israel decided to launch a preemptive military strike against Iran.
Romney said in a speech Sunday the United States and Israel would remain staunch allies through the ongoing dispute with Iran, but did not delve into specific steps he would take if elected president in November.
The presumptive Republican nominee told CBS he did not want to "distance" himself from official U.S. foreign policy while on foreign soil. At the same time, he reiterated that a nuclear Iran was unacceptable.
"That is something which is dangerous to the world," said Romney. "It's a national security threat to America and it threatens the very existence of Israel."
Iran has insisted its secretive nuclear program is aimed at peaceful electricity production but the United States, Israel and other nations say it is more likely meant to develop nuclear weapons.
Puzzle-maker slips 'Murdoch Is Evil' into Rupert Murdoch's Sunday Telegraph
Campus cop fatally shoots Texas student during traffic stop