"The discussions in Geneva were really surprising, and if the promises given [to the West] are realized, then the hard work of thousands of scientists would be ruined," the Kaleme Web site quoted Mousavi as saying in reference to the nuclear fuel plan.

He also warned that the failure of the talks would have far-reaching consequences for Iran.

"If we cannot keep our promises, then it would prepare the ground for harder sanctions against the country," Mousavi said in a meeting Tuesday with Shiite Muslim cleric Mehdi Karroubi, who also ran against Ahmadinejad in the June election, Kaleme reported.

"All of these are the results of adventurism and bypassing of national interests and principles in our foreign policy," said Mousavi. He pointed out that his supporters are currently being prosecuted for alleged ties with the United States and other Western nations.

"The interesting part is that the revolutionary and serving sons of our nation are accused of relations and affiliations with the West, while they [government leaders] repeatedly and openly humiliate themselves in front of the U.S.," Mousavi said.