WASHINGTON — United States Special Operations commandos carried out a risky raid in northwestern Syria on Saturday against a senior terrorist leader there, two senior administration officials said late Saturday.
A senior American official said commandos and analysts were still seeking to confirm the identity of the terrorist, who the officials said was killed in the operation when he exploded his suicide vest.
But a person close to President Trump said that the target of the raid was believed to be the leader of the Islamic State, Abu Bakr al-Baghdadi. A senior administration official said that the president had approved the mission.
Officials said the raid was in Idlib Province, hundreds of miles from the area where Mr. Baghdadi was long believed to be hiding along the Syrian-Iraqi border. Idlib is dominated by jihadist rebel groups hostile to him.
Mr. Trump teased that a major event had occurred with a tweet devoid of context shortly before 9:30 p.m. “Something very big has just happened!” the president wrote.
Roughly 90 minutes later, a White House spokesman, Hogan Gidley, said that Mr. Trump would deliver a statement at 9 a.m. on Sunday, an unusual time for formal presidential remarks, and one that coincides with the morning news shows. Mr. Gidley declined to elaborate on what Mr. Trump planned to say.
An American official said that commandos from the Army’s elite Delta Force carried out the mission with the C.I.A. providing intelligence and reconnaissance information on the ground.
Pentagon spokesmen declined to comment but said that in addition to Mr. Trump’s statement on Sunday morning, Defense Secretary Mark T. Esper would appear on the morning shows to discuss developments in Syria. Mr. Esper had not been previously scheduled as a guest.
The raid came as the United States continued to withdraw hundreds of troops from northern Syria who had been conducting counterterrorism missions, while sending in several hundred other forces to guard eastern oil fields in Syria against the Islamic State.
Some analysts expressed skepticism that Mr. Baghdadi would be hiding in Idlib, in northwest Syria. He was always thought to be hiding in the borderlands between Iraq and Syria in the heart of the Islamic State’s former caliphate, or religious state.
The dominant group in Idlib is a jihadist organization called Hayat Tahrir al-Sham, formerly known as the Nusra Front, which was linked to Al Qaeda. They and ISIS are rivals so it would be surprising if Mr. Baghdadi were hiding in Idlib. But hundreds of ISIS fighters fleeing Iraq and northeastern Syria are believed to be hiding in the northwest, some even joining their former Qaeda rivals, so analysts said it is possible Mr. Baghdadi found refuge with them.
The Islamic State has not had a significant presence in Idlib for many years since they were chased out of northwest Syria by angry rebels.
An American official said on Saturday night that senior military officials had decided that, with American forces largely withdrawing from Syria, commandos should take action quickly to try to kill or capture senior terrorists in northwest Syria before the United States lost that ability.
Mr. Baghdadi, the cunning and enigmatic black-clad leader of the Islamic State, transformed a flagging insurgency into a global terrorist network that drew tens of thousands of recruits from 100 countries.
He has been the target of a yearslong, international manhunt that consumed the intelligence services of at least four different countries, and is believed to hew to extreme security measures, even when meeting with his most-trusted associates.
Much of the world first learned of Mr. Baghdadi in 2014, when his men overran one-third of Iraq and half of neighboring Syria and declared the territory a caliphate, claiming to revive the Muslim theocracy that ended with the fall of the Ottoman Empire.
At its peak, the group’s black flag flew over major population centers, including the Iraqi city of Mosul, with a population of 1.4 million.
In these territories, the group known variously as ISIS, ISIL and Daesh imposed its violent interpretation of Islam.
Security officials say that Mr. Baghdadi was arrested near the Iraqi city of Falluja at the home of his in-laws in January 2004.
The target of the raid was his brother-in-law, who had taken up arms against the American occupation. Mr. Baghdadi was swept up in the raid, considered little more than a hanger-on at that point, officials said. He spent 11 months in a detention center at Camp Bucca.
Some analysts have argued that it was Mr. Baghdadi’s time in American custody that radicalized him. But those who were imprisoned alongside him say he was already committed to violence when he entered the sprawling prison camp.
Pentagon records indicate that Mr. Baghdadi was released in late 2004, a failure of intelligence that would come to haunt American officials.
For years, he disappeared from view. Then in 2009, security forces recovered a cache of documents in a safe house used by the militants and found the name “Abu Dua” on the group’s personnel list, the nom de guerre Mr. Baghdadi was using at the time.
In May 2010, the insurgents announced their new leader: It was Abu Dua, who now introduced himself to the world as “Abu Bakr al-Baghdadi.”
There were numerous near-misses in attempts to arrest him. But with each close call, Mr. Baghdadi became more circumspect, more obsessed with security and more untrusting. He is believed to have stopped using cellphones over a decade ago, relying exclusively on hand-delivered messages.
In 2014, when he ascended the marbled pulpit of a mosque in Mosul to declare the caliphate, it was the first time he video appeared that showed his face uncovered.
Mr. Baghdadi’s reclusiveness fed rumors of his demise, with many news media outlets carrying speculative reports of his death, all of which proved to be untrue. Each time, he resurfaced in audio recordings, thumbing his nose at the world.
Eric Schmitt reported from Washington, and Maggie Haberman and Rukmini Callimachi from New York.
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