With tacit American support, the Israeli military targeted an advanced Iranian air-defense system at a Syrian base last week, said intelligence officials and others briefed on the matter, the latest sign the Trump administration is working with Israel to blunt Tehran’s expanding influence in the Middle East.
After conferring with President Donald Trump, Israeli Prime Minister Benjamin Netanyahu ordered a strike on the newly arrived antiaircraft battery to prevent Iranian forces from using it against Israeli warplanes carrying out increasing numbers of operations in Syria, some of these people said.
Israeli officials told the Trump administration about the planned strike in advance so that the U.S. was aware of their plans to directly target an Iranian base, according to two people briefed on the plans.
Israeli leaders have kept silent about the strike, but Russia, Iran and Syria all accused Israel of carrying it out. Information provided by intelligence officials and others briefed on the strike offered new details on the specific target, Israel’s goals, and the discussions with Washington.
Last week’s attack marked a significant escalation in Israel’s efforts to prevent Iran from cementing its military presence in Syria, where Tehran and its Hezbollah ally provide vital support for President Bashar al-Assad.
Iran has threatened to hit back at Israel, which is bracing for a wider clash with Tehran. A protracted confrontation between the two Middle East rivals could create a dangerous new dynamic in Syria, where Mr. Trump is looking to extricate American forces from a convoluted conflict that shows no signs of coming to an end soon.
Some U.S. officials worry that a broader Israel-Iran fight in Syria could trigger new spasms of conflict that envelop Lebanon and Israel.
The region is roiled by a toxic stew of conflicting alliances surrounding the war in Syria. Iran, Hezbollah and Russia are helping Mr. Assad push rebels to the brink of defeat. More than 2,000 U.S. troops whose mission is to defeat Islamic State militants work alongside Kurdish and Arab forces in Syria. And Turkey has seized another section of Syria as Ankara moves to contain Kurdish ambitions.
U.S. support for the Israeli strike comes as Mr. Trump, wary of an open-ended fight in the Middle East, is leaning on allies—especially Israel and Saudi Arabia—to play a bigger role.
Iran has denied it is seeking to establish bases in Syria, but has said its forces will remain in the country to defend Mr. Assad’s government.
Syria’s government is on alert for more American or Israeli strikes, and on Tuesday launched missiles and sounded air-raid sirens for what turned out to be a false alarm.
Since taking office last year, Mr. Trump has allied himself with Mr. Netanyahu, giving Israel strategic backing for its efforts to target Iran’s expeditionary military operations in Syria, according to the people familiar with the discussions.
The Syrian base targeted by the Israeli airstrike has become an elevated concern for Israel. Known as T-4, Syria’s largest air force base hosts government forces, Russian fighters and a growing Iranian drone fleet used for reconnaissance and potential attacks, defense analysts said.
In February, Israel accused Iran’s Quds Force of using the base to launch a drone into Israel. An Israeli helicopter shot down the drone, which Israel said last week was fitted with explosives.
Israeli F-16s followed up by carrying out airstrikes that destroyed the suspected command post at the T-4 base operating the drone.
After the strikes, an Israeli jet was shot down by Soviet-era, surface-to-air missile, marking the first time one of Israel’s jets had been brought down in combat since 1982.
In response to the February strike, Iran moved to beef up its air defenses at the base. Earlier this month, Israel tracked an Iranian plane that flew a Tor missile system from Tehran to the Syrian base.
Israel moved quickly to destroy the new air defense system before Iranian forces could set it up, intelligence officials said.
Mr. Netanyahu called Mr. Trump two weeks ago to talk about Iran and Syria. Without going into detail, the White House said the two men “agreed to continue their close coordination on countering Iran’s malign influence and destabilizing activities.”
Mr. Netanyahu also told Mr. Trump about the planned strike on the Iranian base, said one person briefed on the call, but Israeli and American officials declined to provide any details.
The Israeli strike came five days later, on April 9. Israel destroyed the antiaircraft system at the Syrian base and a hanger used to shelter drones, triggering denunciations from Syria, Russia and Iran. Iranian media said seven Iranian military advisers were killed, including an officer who oversaw drone operations.
Israel had begun planning the strike before a suspected Syrian chemical weapons attack on April 7. As Mr. Trump vowed to hit Mr. Assad for the chemical attack, Israel launched its strike against Iran, triggering speculation for a time that the U.S. had carried out the April 9 airstrike. An attack against chemical weapons facilities by the U.S., France and Britain followed on April 14.
Mr. Netanyahu considers permanent Iranian military bases in Syria a “red line.” Israel and the U.S. both are concerned about Iran using Syria to attack Israel and to establish a weapons supply route running from Tehran to Lebanon.
Iran is flying weapons into Khmeimim Air Base, a well-defended Russian base on the Mediterranean coast, according to intelligence officials briefed on the matter.
Iran also has rebuilt a presence at Damascus International Airport after a 2015 airstrike, and the airport also now serves as a base for Iran’s Quds Force, which has built underground storage tunnels to safeguard weaponry, these people said.
In total, Iran now works from five airfields in Syria, including Aleppo, Deir Ezzour, T-4, Damascus airport and Sayqal, located south of the capital, according to intelligence officials. At each, Iranian military transport aircraft bring weapons for Hezbollah or missiles and drones specifically for Iranian forces, these officials said.
“It’s the most serious establishment of Iranian military positions close to Israel’s border than [Israelis] have ever seen,” said James Sorene, chief executive of Bicom, a U.K.-based think tank.
The Trump administration says it will work to push Iran out of Syria, but Mr. Trump’s national security team is divided over how. The Pentagon repeatedly has dismissed suggestions that it plans to turn its focus in Syria from defeating Islamic State to challenging Iran. Pentagon officials worry that Tehran will target American forces across the region if the U.S. directly challenges Iranian forces in Syria.
However, U.S. forces in Syria haven’t always been able to avoid confrontations with Iran. Last year, U.S. warplanes shot down two Iranian-made drones viewed as a threat.
Dore Gold, former director general of Israel’s foreign ministry and president of the Jerusalem Center for Public Affairs, said it is increasingly important that Israel “clarify its red lines in Syria in the event that the U.S. disengages from the region.”