Members of a U.N. group use binoculars to look toward the Syrian side of the Golan Heights on Sept. 5, 2014. (Jack Guez/AFP/Getty Images)

President Trump’s call to recognize Israeli sovereignty over the Golan Heights fired up Middle East tensions on Friday and complicated a U.S. push to roll back the growing regional influence of Iran and its allies, which say their military expansion is necessary to counter Israeli threats to Arab lands.

Syria, which lost control of a third of the strategic Golan region to Israel during the 1967 Arab-Israeli war and has not given up hope of getting it back, slammed the U.S. policy shift as “an act of aggression” and vowed to regain control of the area “by all available means.” 

“The Golan was and will remain a part of Arab Syria,” Syria’s Foreign Ministry said in a statement.

Syrian allies Russia and Iran also condemned the U.S. decision, conveyed in a tweet by Trump on Thursday, as contrary to international law and United Nations resolutions. Many U.S. allies, including the European Union, Egypt and Turkey, also expressed opposition to the shift, which overturns decades of U.S. policy on the status of the Golan Heights.

The White House endorsement of Israeli sovereignty over the plateau fulfills a request from Israeli Prime Minister Benjamin Netanyahu and came less than three weeks before the April 9 election in which Israeli voters will decide whether to reelect their prime minister for a fifth term. Trump’s decision was widely welcomed by Israelis, but also triggered criticism that he was interfering in a close election campaign to help Netanyahu.

In Lebanon, the furor over the Golan statement overshadowed a visit by U.S. Secretary of State Mike Pompeo intended to rally support for the Trump administration’s effort to roll back Iran’s expanded influence across the Middle East. Pompeo delivered a tough warning to Lebanese officials that they would have to choose between their accommodation with the Iran-backed Hezbollah movement and their alliance with the United States. 

“The Lebanese people face a choice: Bravely move forward or allow the dark ambitions of Iran and Hezbollah to dictate your future,” he said after a meeting with Lebanon’s Foreign Minister Gebran Bassil.

Pompeo’s message was blunted, however, by concerns that Trump’s decision risks a confrontation in the tense Golan region, reinforcing Hezbollah’s argument that its military role in the region is justified. 

“This tweet is very dangerous, and it will lead to more chaos in the region,” said Mohammed Obaid, a Lebanese analyst who is close to Hezbollah.  

Syria has made no military effort to regain the Golan since the 1973 Arab-Israeli war, and its tired army, depleted after eight years of battling Syrian rebels, is no match for Israel’s superior military capabilities, making it improbable that Trump’s assertion will trigger an outright war. 

The Syrian conflict has brought Iranian military advisers and Iranian-backed militias, such as Hezbollah, into the strategic Golan area on Israel’s borders. Those forces have on several occasions fired rockets into Israel, prompting Israeli retaliatory strikes.

Pompeo’s mission to convince Lebanon to turn against Hezbollah was never likely to succeed given the group’s entrenched role both as a political player and the most powerful armed group in the country, according to Hilal Khashan, a professor of political science at the American University of Beirut. 

The announcement of the U.S. policy shift on the eve of Pompeo’s visit doomed the effort to failure, handing a propaganda victory to Hezbollah, he said.

“This measure will boost Hezbollah by justifying its military presence on the Golan and giving it an excuse for continued expansion,” Khashan said. “Hezbollah will benefit by telling everyone: ‘Our pledge to maintain our military arsenal is justified, the war is not over.’ And it will weaken those who would like to see Hezbollah eventually disarmed.” 

Lebanese leaders responded to Pompeo’s warning by pointing out that Hezbollah is an elected member of the Lebanese parliament with ministers in the Lebanese government. In a tweet, Bassil said he told Pompeo that Lebanon regards Hezbollah as a political party and not a terrorist organization. 

 “It has huge popular support and elected MPs,” he said. “We do not want our relations with America to be impacted. We hope to work together to solve the problem.” 

 The reverberations of Trump’s tweet, meanwhile, rippled around the Middle East. Iran, which backs a range of Shiite militias that have threatened military action to reclaim the Golan for Syria, warned that the U.S. policy shift heralded a “new crisis” for the region, according to a statement by Iran’s Foreign Ministry.

Turkish President Recep Tayyip Erdogan echoed the warning in a speech in Istanbul condemning Trump’s “unfortunate remarks” he said would push the Middle East “to the brink of a new crisis.”

“We cannot allow the legitimization of the occupation of the Golan Heights,” he said.

In a separate dispute involving the Trump administration and its NATO ally Turkey, Erdogan’s insistence on proceeding with a purchase of Russian S-400 missiles, over Washington’s objections, is threatening the cohesion of the transatlantic alliance that has defined the U.S.-Turkish relationship for the past 60 years.

In Israel, Trump’s Golan declaration prompted criticisms about election interference.

 “It’s clear that Netanyahu has managed to influence Trump to do this for his own electoral benefit,” said Jonathan Rynhold, a professor in political science at Israel’s Bar-Ilan University. “It is clear intervention in the Israeli electoral process.”

In an interview with Fox Business aired on Friday morning, Trump denied he was trying to help Netanyahu politically. “I wouldn’t even know about that,” Trump said. “I have no idea. I hear he is doing okay?”

The president said he had been thinking about the move for a “long time.”

But the new U.S. policy on the Golan Heights adds to the list of wins that Netanyahu has been touting, including U.S. steps to scrap its participation in the nuclear deal with Iran and the transfer of the U.S. Embassy to Jerusalem, which Washington recognized as Israel’s capital. 

The timing is particularly favorable for Netanyahu, as his political opponents have been trumpeting corruption allegations against him. His main election opponents in the Blue and White party, headed by former army chief of staff Benny Gantz and Netanyahu’s longtime rival Yair Lapid, have called for an investigation into allegations that the prime minister made $4.3 million in connection with an Israeli submarine contract with a German firm.

The Israeli attorney general has already announced his intention to indict Netanyahu in three other corruption cases, pending a hearing in which the prime minister can offer a defense. Netanyahu has not been named as a suspect in the submarine case, known as Case 3000, but his close aides and personal lawyer have.

Netanyahu has strongly denied any wrongdoing in connection with the four cases and on Friday instructed his lawyers to sue Gantz and Lapid for libel.

In the Israeli-controlled portion of the Golan Heights — whose estimated 50,000-strong population is divided roughly equally between Israeli Jewish citizens and Arabic-speaking Druze of Syrian descent — some Druze expressed dismay at Trump’s announcement.

“People in the Golan are very angry with the decision,” said Ramez Rabah, a tribal and religious Druze leader in the town of Majdal Shams. 

Morris reported from Jerusalem. Sufian Taha in Jerusalem, Kareem Fahim in Istanbul and Carol Morello in Washington contributed to this report.