JERUSALEM -- Israel's surprising strike at an alleged Islamic Jihad base in Syria -- in response to a suicide bombing by the group -- threatens to widen the conflict with the Palestinians and draw in an old enemy, whose frontier with Israel has been quiet for 30 years.

The strike early Sunday underscores Israel's frustration with its inability to end three years of unrelenting Palestinian militant attacks despite a massive and continuing military effort in the West Bank and the Gaza Strip.

If Syria does not respond militarily to the strike -- as it appears it won't -- Israel will have succeeded in serving notice that it is prepared to strike at nations supporting militants as part of its campaign to halt violence against the Jewish state.

"The attack today is to show the Islamic Jihad they will receive no sanctuary, regardless of where they are," said Raanan Gissin, an adviser to Israeli Prime Minister Ariel Sharon. "This is also a very clear message to Syria. Despite U.S. demands to close all the bases, nothing has been done. They have to comply with what they promised."

Syria has been accused by the United States of harboring terror groups, allowing militants to cross its border into Iraq to kill U.S. soldiers and seeking non-conventional weapons.

In its announcement of the air strike, which reportedly injured one guard, Israel also lashed out at Iran, accusing it of financing and directing Islamic Jihad.

Israel has been trying to shift world attention to what it says is Tehran's support for Palestinian militant groups, both with weapons and money. Iran is suspected of trying to develop nuclear weapons, but its involvement with militants has been less of an issue.

After Saturday's suicide bombing by Islamic Jihad, in which 19 bystanders including several children were killed in a crowded beachfront restaurant in Haifa, the Israeli government was under strong pressure at home to deliver a dramatic response.

In past retaliation for suicide attacks -- there have been more than 100 since the fall of 2000 -- Israel has imposed strict travel bans on Palestinians, raided towns to arrest fugitives, demolished homes and killed militants in targeted attacks, and restricted the movement of Palestinian leader Yasser Arafat. The result, at best, has been to slow the pace of bombings.

After Saturday's bombing, there was talk again about expelling Arafat. Israel's Cabinet approved such a step in principle last month, after twin bombings that killed 15 people. However, the United States opposes expulsion and even some of Israel's own security chiefs warn it would be counterproductive.

So Israel opted instead for the air strike, the first Israeli attack deep into Syrian territory in three decades. The response appeared dramatic enough to satisfy the Israeli public without putting Israel's ties with Washington, a major asset, at risk.

Israel apparently calculated that Syria would not retaliate and that the United States, upset with Syria for a failure to confront militants, would not be overly angry at the bombing. The Bush administration called for restraint by both sides.

But the move was not without risk and could destabilize what has been a relatively peaceful frontier. There has been relatively little fighting since the 1973 Yom Kippur War -- which broke out 30 years ago today -- when Syria tried to reclaim the Golan Heights that it lost in the 1967 Mideast War.

The two nations did fight in Lebanon in the 1980s. And Iranian-funded Hezbollah militants, at times acting as a Syrian proxy, have often launched missiles into northern Israel from Lebanon.

The United States, France and other countries have often served as intermediaries to try to defuse tensions between Israel and Syria.

Syrian President Bashar Assad, who took office in July 2000 after the death of his father, Hafez, has not been tested in battle against Israel and is widely seen as unlikely to risk a major confrontation now.

Though Syria has 380,000 active duty soldiers and 520 combat aircraft to Israel's 185,000 active troops and 628 combat aircraft, according to 2002 statistics, military analysts say Israel's military is far stronger than Syria's.

"Syria is not in a military position to do serious damage to Israel without massive Israeli response," said Gerald Steinberg, a political science professor at Bar Ilan University.

Other than the Palestinians, Syria remains almost the last of Israel's traditional enemies. Israel has signed peace treaties with Egypt and Jordan, and another major threat to Israel, the Saddam Hussein regime in Iraq, was eliminated by U.S. forces this year.

Now Syria is caught between U.S. troops in Iraq on their eastern border and Israeli forces to the southwest.

The United States itself has deeply strained ties with Syria, accusing it of supporting Hezbollah, Hamas and Islamic Jihad -- groups the United States considers terrorists.

The United States also accuses Syria of letting foreign fighters into Iraq to attack American troops, and the recent arrest of two U.S. servicemen with links to Syria have led to U.S. suspicions that Damascus is spying on Washington.

In the past, Israel has held Syria accountable for Hezbollah's attacks from Lebanon. Now it appears to be holding it accountable for the actions of Palestinian militant groups who have operations in Syria.

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EDITOR'S NOTE: Ravi Nessman is an Associated Press correspondent based in Jerusalem.