Iran will respond with threats of its own to intensifying warnings of military attacks and Western sanctions, its supreme leader said Friday in remarks particularly aimed at archfoe the United States.

"The United States and others have to know -- and they know -- that, in response to threats of oil embargo and war, we have our own threats which will be implemented at the right time, if necessary," said Ayatollah Ali Khamenei.

His comments, in a televised speech as he led traditional Friday prayers in Tehran, came amid heightened speculation that Israel was contemplating air strikes against Iranian nuclear facilities, with or without US help.

The West has also ramped up sanctions aimed at severely curbing Iran's vital oil exports.

Khamenei, who spoke as part of events marking the anniversary of his country's 1979 Islamic revolution, focused on US warnings that it was mulling "all options" -- including war -- to undercut Iran's suspect nuclear programme.

"They have threatened that 'all options are on the table'... Threats of war are detrimental to the United States, and carrying out a war would be 10 times more detrimental for that country," he said.

The United States and much of the West fear Iran is trying to develop the capability to make atomic weapons as part of its nuclear drive, despite Tehran's repeated assertions the programme is for exclusively peaceful purposes.

Western economic sanctions have ramped up against Iran over the past three months, since the UN nuclear watchdog, the International Atomic Energy Agency, issued a report saying it had evidence the Islamic republic appeared to be researching atomic warheads.

The United States and the European Union have imposed sanctions on companies dealing with Iran's financial sector, and an EU ban on Iranian oil imports is being phased in over the next five months.

Despite a depreciation of Iran's currency, the rial, and increased difficulty in receiving payment for oil shipments, Iranian officials have dismissed the effects of the sanctions.

"The sanctions in fact benefit us," Khamenei said. Because of them, "we have fallen back on our domestic potential," he said.

He said the aim of the sanctions, to force Iran to halt its nuclear activities, was not going to be met.

"They (Western nations) say they impose sanctions, crippling sanctions, to force us to retreat, in the nuclear field and other areas... But we haven't retreated," he said. "Iran will not retreat."

The worsening international showdown has led to increased speculation Israel is poised to order air strikes on Iranian nuclear facilities.

A column in the Washington Post newspaper said US Defence Secretary Leon Panetta believes there is a "strong likelihood" that Israel will conduct those strikes in April, May or June despite US reservations.

Panetta told reporters while he was in Brussels to attend a NATO meeting, that he was not going to comment on the opinion piece.

"Israel indicated they're considering this (a strike), we've indicated our concerns," he said.

Israeli officials have said they believe they have a window of just a few months in which their warplanes could hit Iran with any chance of degrading its nuclear programme.

They also say they view the prospect of Iran developing nuclear weapons as an "existential" threat -- meaning one that threatens the very existence of the Jewish state.

Israel is currently the Middle East's sole if undeclared nuclear power.