TEHRAN, Iran – Iran warned that any strike on its nuclear facilities would draw a swift and crushing response and called yesterday for an expansion of its newly emerging strategic alliance with Syria to create a powerful united Islamic front that could confront Washington and Israel.

Such an expansion appears unlikely to go far, because many key Arab states – Egypt, Jordan, and Saudi Arabia – are close Washington allies and have long been suspicious of Iran’s Shiite Muslim clerical regime.

Still, the statements were another sign of the tense situation, coming a day after Syria and Iran declared they would form a united front against any threats, and a mysterious explosion near a nuclear facility in southwestern Iran that initially was reported as a missile strike but later was attributed to construction work on a dam.

Iran’s overtures to other Muslim countries in the Middle East reflect its concern about American pressure to drop all its nuclear ambitions. With Syria under similarly strong American scrutiny – in its case for its role in Lebanon and as an alleged sponsor of terrorism – the two nations are trying to diminish Washington’s efforts to isolate them.

The Bush administration has so far applied only diplomatic pressure, but has talked tough. President Bush has labeled Iran part of an “axis of evil” with North Korea and prewar Iraq.

Secretary of State Rice said February 4 that a military strike against Iran was “not on the agenda at this point,” but Mr. Bush has said he would not rule out any option.

Mr. Bush said yesterday that America would support Israel “if her security is threatened.”

Israel has warned that it may consider a pre-emptive strike against Iranian nuclear installations along the lines of its 1981 bombing of an unfinished Iraqi nuclear reactor near Baghdad. America accuses Iran of having a secret program to make nuclear weapons; Iran insists its nuclear activities are for peaceful energy purposes.

“If I was the leader of Israel and I’d listened to some of the statements by the Iranian ayatollahs that regarded the security of my country, I’d be concerned about Iran having a nuclear weapon as well,” Mr. Bush said.

Fears that America or Israel will attack Iran or Syria abound in the region, and Iranian Defense Minister Ali Shamkhani was quoted yesterday by state-run radio as saying retaliation would be harsh.

“When the Iranian nation sees our crushing response to the enemy, it should know one of our nuclear or non-nuclear facilities has been attacked,” he said.

Iran’s powerful former president Hashemi Rafsanjani, speaking after meeting Syrian Prime Minister Naji al-Otari, said it was important to strengthen relations among Iran, Syria, Iraq, Lebanon, and other Islamic states in the region, the official Islamic Republic News Agency reported.

Mr. Rafsanjani said America and Israel were trying to create divisions among regional countries, which he said must “stay completely vigilant vis-a-vis the U.S. and Israeli plots.” Mr. Rafsanjani is widely expected to run in June presidential elections.

Iran and Syria long have maintained warm relations. Syria was the only Arab country that remained allied to Iran during the 1980-88 war, and the two countries often coordinate on foreign policy, especially with regard to the Israeli-Palestinian Arab conflict and the American-led war on Iraq.

Iranian President Mohammad Khatami, who also met Mr. al-Otari, said Iran and Syria would safeguard their political relations by strengthening their economic ties, IRNA reported.