Supreme Leader Ayatollah Ali Khamenei said on Friday world powers had been persuaded they could not block Iran's nuclear progress, but he made no mention of a message by US President Barack Obama to his country.
In a separate recorded speech to mark the Iranian New Year, President Mahmoud Ahmadinejad said global powers had reached a "dead end." But he also did not mention Obama's videotaped offer of a "new beginning" of diplomatic engagement.
Iran and the United States are embroiled in a dispute over Tehran's nuclear program, which Washington and its allies suspect is aimed at making bombs. Tehran says the program is for peaceful power purposes.
Khamenei hailed tests last month of Iran's first nuclear power plant, at Bushehr in the country's south, as an important development.
"This is the result of the progress of our scientists ... which persuaded the whole world that the path of Iran's nuclear progress could not be blocked," said Khamenei, Iran's top authority with final say on all matters of state.