(REUTERS) -- Supreme Leader Ayatollah Ali Khamenei has warned that Iran will not submit to foreign pressures to cease its nuclear program and repeated threats against Israel and western powers in a speech on Friday.

Khamenei’s speech, to mark the anniversary of the 1979 revolution, is the first direct response from a senior Iran official to the growing threat posed by western sanctions and potential Iranian retaliations.

The United States and the European Union have intensified sanctions on Iran’s oil exports in order to fore Teheran to abandon its nuclear weapons program. Speculation has risen that Israel may be planning to conduct a surgical strike against Iranian nuclear sites, as they have previously done in Iraq and Syria.

"Threatening Iran and attacking Iran will harm America… Sanctions will not have any impact on our determination to continue our nuclear course,” Khamenei said in a speech on live television.

“In response to threats of oil embargo and war, we have our own threats to impose at the right time. I have no fear of saying that we will back and help any nation or group that wants to confront and fight against the Zionist regime [Israel]."

He further warned that a military strike on Iran would backfire against the west and vowed that the "painful and crippling" Western sanctions will only serve to increase Iran’s resilience.

"Americans say all options are on the table even the option of military strike [against Iran],” he declared.

“Any military strike is ten times more harmful for America. Such threats show that they have no sufficient discourse against Iran's logic and discourse."

He added: “The Zionist regime [Israel] is a true cancer tumor on this region that should be cut off. And it definitely will be cut off.”

Meanwhile, Israel has stepped up the rhetoric against Iran.

Defense Minister Ehud Barak has explicitly stated that Israel may consider a surgical strike on Iran.

“If sanctions don’t achieve the desired goal of stopping [Iran’s] military nuclear program, there will be a need to consider taking action,” he said.

On Thursday, Israeli Vice Premier Moshe Ya’alon vowed that Iran has to be stopped “one way or another.”

Israel’s Military Intelligence Maj.-Gen. Aviv Kochavi has estimated that Iran has enough enriched uranium to manufacture four nuclear weapons. But he added that it would likely take the Iranians a year to make a crude nuclear device, and at least another year to manufacture a nuclear warhead which would be attached to a ballistic missile.

The U.S., a strong ally of Israel, is gravely concerned about a potential strike on Iran. The Washington Post reported that U.S. Defense Secretary Leon Panetta thinks Israel may attack Iran in April, May or June.