Speaking at the Foreign Press Association in Jerusalem Monday, Barak said while the international sanctions imposed on Iran have been effective, they have failed to halt its race to achieve nuclear power, The Jerusalem Post reported.
The defense minister said he was not filled "with confidence."
"I may sound pessimistic but the state of Israel cannot afford to be duped," Barak said.
Iran is scheduled to conduct a second round of talks with the United States, Russia, China, Britain, France and Germany (known as the P5+1 countries) May 23 in Baghdad, Iraq.
Yaacov Amidror, Israel's national security adviser, meanwhile, is visiting Europe where he is expected to hold sensitive talks with European officials ahead of the next session of talks with Iran, Haaretz reported Tuesday.
A senior Israeli official said Amidror's meetings are "extremely sensitive," indicating he hopes to find out as much as possible about the first round of talks and will seek to learn of the negotiating team's strategy for the next round, the newspaper said.
Last month, Amidror traveled to Moscow and met with Foreign Minister Sergei Lavrov, who stressed Russia opposes any unilateral military action by Israel in Iran, saying such a move would have destructive consequences throughout the Middle East, the newspaper said.