Iranian President Mahmoud Ahmadinejad has said the Islamic Republic would soon announce "very important" achievements in the nuclear field, state TV reported.
He was speaking on the 33rd anniversary of the Islamic revolution.
Tens of thousands of Iranians joined state-organised rallies across the country to mark the occasion.
Demonstrators carrying Iranian flags and pictures of Supreme Leader Ayatollah Ali Khamenei chanted "Death to Israel" and "Death to America".
"In the coming days the world will witness Iran's announcement of its very important and very major nuclear achievements," Mr Ahmadinejad told a crowd at Tehran's Azadi (Freedom) Square in a speech relayed live on state television.
He gave no details.
Tension with the West over Iran's disputed nuclear work has risen in recent weeks.
The US and its European allies have imposed new sanctions to try to force Tehran back to talks before it produces enough nuclear material for an atomic bomb.
Iran says its nuclear programme has only peaceful purposes.