Iranian President Mahmoud Ahmadinejad said Sarturday his country would soon unveil "very important" nuclear achievements and that the West's efforts to slow it down were futile.
Meanwhile, Hamas' leader in Gaza, Ismail Haniyeh, said the group would never recognize Israel. The two were speaking in Tehran on the 33rd anniversary of the Islamic revolution.
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," Ahmadinejad told a crowd at Tehran's Azadi Square in a speech broadcast live on state television. He gave no details.
"The world should know that despite all pressures, Iran will not withdraw one inch from its principles and [nuclear] rights," he said.
"All countries have put pressure on us for not obtaining nuclear know-how, but all these pressures were futile. We not only now have the nuclear know-how but also are capable of providing for our [nuclear] needs by our own local experts."
In recent weeks, the United States and its European allies have imposed new sanctions to try to force Iran back to talks. Iran says its nuclear program has only peaceful purposes.
The United States and Israel have not ruled out military action to prevent Iran from obtaining nuclear weapons. Tehran has warned of a "painful" answer, saying it would hit Israel and U.S. bases in the Gulf as well as block the vital oil shipping route through the Strait of Hormuz.
Haniyeh, meanwhile, maintained his hard stance on Israel. "They [the West] want from us to stop resistance and acknowledge Israel, but I herewith announce that this will never happen," Haniyeh said through an interpreter.
"Our message and the message of all those who lost their blood in the Palestinian lands is that all occupied lands will eventually be liberated from Israeli occupation."