The United States has carried out an operation targeting ISIS chief Abu Bakr al-Baghdadi, a US official told news agency Reuters, speaking on condition of anonymity.
The official did not disclose details of the operation and did not say whether it was successful. Other US officials contacted by Reuters declined comment.
Newsweek, citing a US Army official briefed on the result of the operation, said al-Baghdadi was killed in the raid.
The official did not disclose details of the operation and other US officials contacted by Reuters declined to comment. The Pentagon did not immediately respond to a request for comment.
White House spokesman Hogan Gidley announced late on Saturday that Trump would make a "major statement" at 9 a.m. EST (1300 GMT) on Sunday. Gidley gave no further details.
The president gave an indication that something was afoot earlier on Saturday night when he tweeted without explanation, "Something very big has just happened!"
Trump has been frustrated by the U.S. news media's heavy focus on the Democratic-led impeachment inquiry, which he calls an illegitimate witch hunt.
He has also faced withering criticism from both Republicans and Democrats alike for his U.S. troop withdrawal from northeastern Syria, which permitted Turkey to attack America's Kurdish allies.
Trump was expected to make the statement in the White House Diplomatic Reception Room, which he has used to make a number of major announcements.
Just last week he used the same room to announce that a ceasefire between Turkey and the Kurds had taken hold.
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