DUBAI: Iran’s supreme leader said Thursday that the Islamic Republic would destroy the Israeli cities of Tel Aviv and Haifa if it came under attack from the Jewish state.

“At times the officials of the Zionist regime [Israel] threaten to launch a military invasion but they themselves know that if they make the slightest mistake the Islamic Republic will raze Tel Aviv and Haifa to the ground,” Ayatollah Ali Khamenei said in an address to mark the Iranian new year, Nowruz.

Israel has threatened to take military action against Iran unless it abandons nuclear activities which the West suspects are intended to develop nuclear weapons. Tehran denies this, saying that its nuclear program is only for civilian purposes.

In his televised speech, Khamenei said Iran’s struggles over the past year against international sanctions imposed over its disputed nuclear program resembled a battle and that its enemies had confessed to trying to “cripple the Iranian nation.”

“What happened last year, we need to learn a lesson,” he said, alluding to what he described as Iran’s significant scientific and military advances.

“This vibrant nation will never be brought to its knees.”

Khamenei also called for Iran’s “natural right” to enrich uranium for nuclear energy to be recognized by the world. Western powers have refused, saying Iran had hidden nuclear work from U.N. inspectors and stonewalled their investigations.

Talks between Iran and six world powers – the United States, China, Russia, Britain, France and Germany – are to resume early next month in a further attempt to strike a deal on Iranian nuclear aspirations.

Although not ruling out the possibility of talks with the U.S., Khamenei was also not overly optimistic about the prospect. The two countries severed diplomatic relations after Iran’s 1979 Islamic Revolution.

“I am not optimistic about these talks. Why? Because our past experiences show that talks for the American officials do not mean for us to sit down and reach a logical solution ... What they mean by talks is that we sit down and talk until Iran accepts their viewpoint,” he said.

“Iran only wants its enrichment right, which is its natural right, to be recognized by the world.”

Khamenei said the offer of direct bilateral talks with Iran is an American tactic to deceive the public and impose its will on Tehran.

He added that problems could be resolved if the United States would stop imposing sanctions, harming Iran’s economy and acting against the country’s territorial integrity.

The issue of Iran’s nuclear weapons program has been high on the agenda during U.S. President Barack Obama’s visit to Israel.

Russia said Thursday that Iran and the six powers made progress in expert-level talks this week on the standoff over the issue, but that there was no breakthrough and that backsliding remained a danger.

“This progress is real but it is not sufficient to speak of a definitive shift,” Deputy Foreign Minister Sergei Ryabkov, Russia’s chief negotiator on the Iran issue, said of the talks in Istanbul Monday.

“We cannot say this progress is irreversible. This alarms us a little, but from round to round, we have a more and more businesslike discussion of all the issues,” he told reporters.

In Istanbul, the six powers gave the Islamic Republic more details of proposals made at political-level talks in late February in the Kazakh city of Almaty, where they offered Tehran modest sanctions relief if it curbs its most sensitive nuclear work.

Ryabkov said the sides had “plenty of homework to do” before the next meeting at a political level, in Almaty on April 5-6, but suggested the technical talks had laid some good groundwork.

Russia, which has built Iran’s first nuclear power plant and has better relations with Tehran than do Western powers, has tended to be more upbeat than Western leaders about Iran’s attitude toward the negotiations.

Russia went along with four rounds of U.N. Security Council sanctions against Iran over its nuclear program but opposes further sanctions and has sharply criticized separate Western sanctions, saying they are counterproductive.