"We believe he was killed in a US strike earlier this month," the official said yesterday, speaking on condition of anonymity.
"He was not considered a high-value target (and) we were not specifically targeting him," he added, noting that other IS jihadists may also have been hit.
Also known by his rap name Deso Dogg, Cuspert later went by Abu Talha al-Almani.
He used to rap in Berlin and was one of the most famous Western fighters for the IS group. He was already listed as an Al-Qaeda supporter by the United Nations.
Jihadist sources in April 2014 said Cuspert had been killed in Syria but they later retracted the claim.
Cuspert joined IS jihadists in 2012 and went on to appear in numerous videos from the militant group, including one in November last year "in which he appears holding a severed head he claims belongs to a man executed for opposing ISIL (IS)," the State Department has previously said.
Cuspert had pledged an oath of loyalty to IS leader Abu Bakr al-Baghdadi and was a chief recruiter of German fighters, officials added.
