TEHRAN, Iran >> Iran’s supreme leader pledged Friday to aid any nation or group that challenges Israel and said any military strikes over the Islamic Republic’s nuclear program would damage U.S. interests in the Middle East “10 times over.”

The nationally broadcast comments by Ayatollah Ali Khamenei staked out a hard line in apparent replies to suggestions that military strikes are an increasing possibility if sanctions fail to rein in the Islamic Republic’s nuclear program.

It also may signal that Tehran’s proxy forces — led by Lebanon’s Islamic militant group Hezbollah — could be given the green light to revive attacks on Israel as the showdown between the archfoes intensifies.

The West and its allies fear Iran could use its uranium enrichment labs — which make nuclear fuel — to eventually produce weapons-grade material. Iran insists it only seeks reactors for energy and medical research.

Israel has so far publicly backed the efforts by the U.S. and European Union for tougher sanctions that target Iran’s crucial oil exports. But Israeli leaders have urged even harsher measures and warn that military action remains a clear option despite Western appeals to allow time for the economic pressures and isolation to bear down on Iran.

Although Israel has raised the strongest hints over a military campaign, Khamenei reserved some of his strongest comments for Israel’s key U.S. ally.

“A war itself will damage the U.S. 10 times over” in the region, said Khamenei.

Khamenei claimed Iran, however, could only emerge stronger. “Iran will not withdraw. Then what happens?” asked Khamenei. “In conclusion, the West’s hegemony and threats will be discredited” in the Middle East. “The hegemony of Iran will be promoted. In fact, this will be in our service.”

On Thursday, Israel’s defense minister, Ehud Barak, suggested the world is increasingly ready to consider a military strike if sanctions fail. The head of the country’s strategic affairs ministry, Vice Premier Moshe Yaalon, also suggested Iran’s main military installations are still vulnerable to airstrikes — even as Iran starts up a new uranium enrichment facility deep in a mountainside bunker south of Tehran.

Yaalon’s comments appear to reinforce earlier suggestions by other Israel officials that the window for a possible attack is closing and Israel would need to strike by summer to inflict significant setbacks on Iran’s nuclear facilities. The officials spoke on condition of anonymity under standing guidelines.

At Ramstein Air Base in Germany, U.S. Defense Secretary Leon Panetta said sanctions remain the best approach to pressure Iran. But he told U.S. airmen Friday that Washington keeps “all options on the table and would be prepared to respond if we have to.”

Khamenei answered by repeating Iran’s declarations that it will never roll back its nuclear program, which he had earlier said was now part of the country’s “identity” and a cornerstone of its technological endeavors. On Friday, Iran said it successfully sent a small satellite into orbit in the third such launch in recent years, state media reported.

“From now on, in any place, if any nation or any group confronts the Zionist regime, we will endorse and we will help. We have no fear expressing this,” said Khamenei, using the phrase widely used by Iran’s leader to describe Israel.

Khamenei affirmed that Iran had assisted groups such as Hezbollah and the Palestinian Hamas — a well-known policy rarely stated explicitly by Iranian leaders.

“We have intervened in anti-Israel matters, and it brought victory,” he said, citing the 2006 war between Hezbollah and Israel and nearly three weeks of conflict in the Gaza Strip that began with an incursion by Israel in December 2008.

The Gaza battles ended in a cease-fire, with Israel claiming to have inflicted heavy damage on the militant organization. The war in Lebanon ended with a U.N.-brokered truce that sent thousands of Lebanese troops and international peacekeepers into southern Lebanon to prevent another outbreak.

Khamenei called Israel a “cancerous tumor that should be cut and will be cut” — a remark he has made previously.

In Jerusalem, an Israeli Foreign Ministry spokesman said he wasn’t surprised by Khamenei’s remarks. “It’s the same kind of hate speech that we’ve been seeing from Iran for many years now,” Yigal Palmor said.

Half of Khamenei’s nearly two-hour speech was delivered in Arabic in a clear nod to the Arab world. Iran has applauded the victory of Islamist groups in elections that followed the toppling of authoritarian regimes in Egypt and Tunisia.

The Supreme Leader said the Islamist electoral victories will “weaken and isolate” Israel and represented the failure of U.S. policies. But the uprisings also have threatened Iran’s most important Arab ally, Syrian leader Bashar Assad.

Another potential military flashpoint is the Strait of Hormuz at the mouth of the Persian Gulf. Iran has threatened to close the strategic waterway in response to U.S. and EU sanctions targeting the country’s oil exports, but it has so far taken no steps to disrupt oil tanker traffic. The powerful Revolutionary Guard said it plans naval maneuvers near the strait this month.

Khamenei also warned that Tehran would reveal a letter that it claims President Barack Obama sent the Iranian leadership in an attempt to end the nuclear impasse. The White House has denied that such a letter exists.

An Iranian lawmaker in January claimed that Obama had asked for direct talks with Iran in a secret letter, which also warned Tehran against closing the Strait of Hormuz.

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Murphy reported from Dubai, United Arab Emirates. Associated Press writer Tia Goldenberg in Jerusalem contributed to this report.