Speaking to reporters at the State Department, Kerry said in his first public comments on the matter since taking office last week that Iran knows full well what it needs to do to prove its nuclear intentions are peaceful as it claims.
If it does, Kerry said the international community is prepared to respond positively. If not, he said Iran will only face increased international isolation. He reminded the Iranian leadership that President Barack Obama has taken no options off the table, including military force, to prevent Iran from obtaining a nuclear weapon.
"We are prepared to let diplomacy be the victor in this confrontation over their nuclear program," Kerry said after meeting with Canadian Foreign Minister John Baird. "The president has made it clear that he is prepared to talk about a peaceful nuclear program."
Kerry also said: "Iran has a choice: they have to prove to the world that it is peaceful and we are prepared to sit responsibly and negotiate how they can do that and how we can all be satisfied."
His comments came ahead of a meeting between Iran and senior officials from the five permanent members of the U.N. Security Council and Germany. That meeting is set for Feb. 26 in Kazakhstan.
Kerry also said that Iran's recent revelation that it would vastly increase its pace of uranium enrichment, which can make both reactor fuel and the fissile core of warheads, is "concerning" and "disturbing."
"The president has made it clear that his preference is to have a diplomatic solution, but if he cannot get there, he is prepared to do whatever is necessary to make certain that Iran does not have a nuclear weapon," he said.