Speaking on Fox News Sunday, Brennan said America has multiple measures at its disposal to ensure Iran doesn't become a nuclear power.
"There are a number of things that the United States has available to it to prevent Iran from getting a bomb," the director of the Central Intelligence Agency said.
Iran and six world powers are in negotiations to clinch a landmark deal that would have the country scale back its disputed nuclear program in return for relief from sanctions.
"President Obama has made it very clear that we are going to prevent Iran from having that type of nuclear weapon that they were ... going on the track to obtain," Brennan added.
"So, if they decide to go down that route, they know that they will do so at their peril."
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In response to a question about America's track record in monitoring Iran's nuclear program, Brennan acknowledged that US intelligence had historically been less than ideal on the issue.
"I think we've gone to school on some of those developments over the last decade or so," he said.
"We can now have a better plan and opportunity to verify some of the things that they are saying they are going to do and not do."
Asked about reports of an underground nuclear site near Tehran, Brennan said: "I am confident that we have a good understanding of what the Iranian nuclear program entails."
When asked if he was concerned about the possibility of a regional arms race, Brennan said partners in the Gulf, including Saudi Arabia, are confident the United States can act as a regional security guarantor.
"We are going to keep close communication, I'm confident the Saudis will be a responsible partner and player in the region," Brennan said.