A ministry statement quoted Barak as telling United Nations Secretary-General Ban Ki-moon in talks at the New York headquarters "we must continue to adhere to a policy where no option is off the table," to stop Iran's project.
"We say this and mean it, and recommend that others do the same," Barak said. He added: "We insist on a continuation and strengthening of the pace of economic and financial sanctions on the Iranians."
Israel was conducting its biggest home front defence exercise which it launched on Sunday, preparing the country for missile attacks should conflict erupt with Iran or Arab enemies.
Israeli Prime Minister Benjamin Netanyahu has described the drill as purely precautionary.
Israeli leaders have not ruled out military strikes against Iran, which maintains it is enriching uranium for power generation.
Israel, which experts believe is the Middle East's largest nuclear power, views Tehran's atomic work as a threat, citing Iranian President Mahmoud Ahmadinejad's repeated calls for the Jewish state's destruction.
After talks last month with U.S. President Barack Obama, Netanyahu said he hoped Washington's diplomatic efforts with Tehran succeeded but that he had made it clear "that Israel retains the right to defend itself." (Writing by Allyn Fisher-Ilan; Editing by Jon Hemming)
