Iran has drawn up plans to bomb Israel if it launches an attack on Iranian soil first, military officials say.
Iran says Israel is not able to launch an air attack on its territory
The deputy commander of Iran's air force said that in the "unlikely event" of an Israeli attack, Tehran could respond with air and missile raids.
Israel's foreign ministry said the comments were alarming and showed that the international community should take a "very firm stance" on Iran.
The US dismissed Iran's remarks as "unhelpful" and "not constructive".
Iran denies the claims by Israel and the West that it is trying to acquire nuclear weapons, insisting it wants nuclear power to generate electricity for civilian use.
Both Israel and Washington were responding to the comments made by Iran's air force deputy commander Gen Mohammed Alavi.
Gen Alavi said Israel did not pose a serious threat, as it was not capable of launching an aerial attack on Iran.
"We have drawn up a plan to strike back at Israel with our bombers if this regime [Israel] makes a silly mistake," Gen Alavi told Iran's official news agency Fars in an interview.
Gen Alavi was speaking just two days after French Foreign Minister Bernard Kouchner warned that the world should prepare for war against Tehran over its uranium-enrichment programme.
The UN is considering a possible third round of sanctions against Iran if it refuses to end the programme.
Some analysts have speculated that Israel could seek to launch a pre-emptive strike to destroy Iran's nuclear facilities, where Israel and the West believe Tehran is trying to build a nuclear bomb.
Israel has done it before. Its air force destroyed Iraq's nuclear facilities in 1981.
The US - Israel's ally in the Middle East - has not ruled out military action over the nuclear dispute, with Secretary of State Condoleezza Rice saying "all options" are on the table.
Washington's contingency plans for air strikes on Iran extend beyond nuclear sites and include most of the country's military infrastructure, diplomatic sources told the BBC earlier this year.
It is understood that any such attack - if ordered - would target Iranian air bases, naval bases, missile facilities and command-and-control centres.