Iran (search) threatened this week to attack Israel's nuclear facilities. Israel (search) ominously warned that it "knows how to defend itself." Tensions between the two arch enemies have suddenly escalated, underlining the other great enmity that has been bubbling on the sidelines of the Arab-Israeli conflict for more than two decades.

Suspicions that the Iranian regime is moving forward with a nuclear arms program deeply worry Israel, which considers Iran the greatest threat to the Jewish state. Israeli officials say they want to avoid escalating the situation, however, and there is no sign Israel is building up for an attack like the one that destroyed Iraq's Osirak nuclear reactor (search) in 1981.

Experts say the two countries are unlikely to go to war anytime soon, despite the heated-up rhetoric coming out of Iran and the intensified efforts by Israel to isolate the Iranian regime diplomatically.

Iran and Israel once had close ties, but they have been foes since the 1979 revolution that ousted Iran's shah and installed an Islamic government. Iranian leaders routinely call for Israel's destruction, while Israelis accuse Iran of supporting anti-Israel terrorists.

The heightened tensions arose from the U.S.-led campaign to organize international pressure on Iran to rein in its nuclear program.

While recently confirming they are working with technology that can be used to produce weapons-grade uranium, the Iranians insist their program's sole purpose is the peaceful generation of power and angrily complain about being under siege.

Last month, the commander of Iran's Revolutionary Guards said Iranians would "crush" Israel if it attacked the Persian state. Iranian Defense Minister Ali Shamkhani, upped the ante this week, telling Al-Jazeera television that his government might launch pre-emptive strikes to protect its nuclear facilities if they were threatened.

"We will not sit to wait for what others will do to us," he said, adding that some Iranian generals believe the doctrine of pre-emption is "not limited to Americans."

The warning was seen as aimed at Israel, alluding to the Israeli strike on Saddam Hussein's reactor two decades ago.

A senior Israeli official responded that Israel's government was ready for all eventualities.

"We're not seeking war with Iran. But if a real threat materializes, Israel will know how to defend itself," said the official, who spoke on condition of anonymity, reflecting long-standing Israeli policy of not talking publicly about matters involving nuclear arms.

Israel is widely believed to have nuclear weapons, but never formally confirms or denies it has them. It believes this policy of ambiguity is the best way to deter attack, by scaring regional foes about the possibility of nuclear annihilation while denying those nations a rationale for also seeking such weapons.

Despite the tensions, experts don't foresee things boiling over.

"I think it is a serious confrontation. The issue is who can do what about it," said Cliff Kupchan, vice president of the Nixon Center in Washington and a former Clinton administration official who is an expert on Iran.

"On the Israeli side, it is not clear that they have the military capabilities or intelligence knowledge to significantly set back the Iranian program. The Iranians learned from Osirak to disperse and copy everything they have (in their nuclear program). I don't think that Israel can do much."

Sammy Salama, a research associate at the Center for Nonproliferation Studies at the Monterey Institute of International Studies in California, noted that the military situation is different, too.

"Iraq didn't have any way of striking back," Salama said, alluding to Iran's long-range Shahab-3 missiles, which are capable of reaching Israel. "I think Iran, in essence, is saying, 'We are not Iraq.'"