This week, Mr. Cuspert was transformed again. The American State Department announced Monday that, as “a willing pitchman” for the extremist group’s “atrocities,” Mr. Cuspert was now a “specially designated global terrorist” sought worldwide.
The designation means that Mr. Cuspert, 39, has gone from being a notorious figure in Germany to one recognized everywhere, and it puts him in the cross hairs of American intelligence in the Syrian region.
The potential evidence against him includes a July 2014 video that, a German report says, shows Mr. Cuspert and a pile of corpses in civilian clothes, apparently victims of a battle for control of the much-contested Shaer gas field near Homs in Syria.
“Cuspert has been on the radar for a while, mainly because he’s so high profile,” said a former senior American counterterrorism official, who spoke on the condition of anonymity to discuss confidential intelligence reports.
The announcement in Washington followed declarations by President Obama and Chancellor Angela Merkel of Germany on Monday, during her visit to the White House, about their continuing cooperation in tracking terror suspects and gathering intelligence in the region.
The relationship between Germany and the United States on intelligence-gathering was shaken in 2013 after Edward J. Snowden revealed the extent to which ordinary Germans were affected and Der Spiegel reported that the Americans had eavesdropped on Ms. Merkel’s cellphone.
At the White House on Monday, Mr. Obama appealed to Germans, who are sensitive about government surveillance because of their Nazi and Communist pasts, to trust Americans not to overstep the line. Ms. Merkel, in turn, stressed how Germany relies on the United States’ intelligence-gathering capacity to guarantee public safety.
State Department officials in Washington said on Tuesday that the designation of Mr. Cuspert had been published without fanfare in the American government’s Federal Register on Jan. 27.
Mr. Cuspert, a.k.a. the rapper Deso Dogg, now goes by Abu Talha al-Almani, according to German and American officials.
He became one of the best-known singers of nasheeds, or Islamic devotional music, in German. According to security officials and excerpts from videos posted online, Mr. Cuspert sings of the comradeship of battle.
His themes include martyrdom: “I wish for my death and can hardly wait for it/Armed with bombs and grenades,” goes one song from 2013, according to a report on Mr. Cuspert compiled by security officials in Berlin.
That report concluded that “in just four years, he developed from a respected, but financially not very successful, ‘gangsta rapper’ to an internationally recognized propagandist of jihad and Salafism.”
Mr. Cuspert was born in Berlin to a German mother and a Ghanaian father who soon left the family. His American stepfather, a former soldier, was a strict disciplinarian, and conflicts at home increased until Mr. Cuspert spent five years in a home for troubled children. “I grew up with racism,” he told The New York Times in 2011.
He said he had joined youth gangs because he was in search of an identity. From an early age, he trained in Thai boxing, taekwondo and jujitsu.
His rap career reached its zenith when he went on tour with DMX in 2006.
By 2010, according to Berlin security officials, he had appeared in a video with Pierre Vogel, a well-known Salafist preacher, who asked about rap connections and what might happen if other rappers embraced Islam.
In 2011, when a 21-year-old immigrant from Kosovo, Arid Uka, fatally shot two American airmen at the Frankfurt airport, he said he had opened fire after seeing a video that claimed to show a Muslim woman being raped by men in United States military uniforms. Mr. Cuspert acknowledged posting the video, which Mr. Uka copied. American officials said it was staged.
In 2012, Mr. Cuspert fell in with an Austrian, Mohamed Mahmoud, and they started a group, Millatu Ibrahim, that was banned after a clash with the police. The two men left for Egypt, reportedly heading for Mali, but landed eventually in Syria.
There, according to German intelligence officials, Mr. Cuspert suffered head wounds in battle in September 2013, but after hospitalization in Turkey returned to the fighting last spring.
The Berlin report on Mr. Cuspert, published last September, concluded with mention of the video that it said showed him among the pile of corpses.
Frauke Köhler, a spokeswoman for the federal prosecutor’s office in Germany, declined to confirm a news report that Mr. Cuspert was being investigated on suspicion of committing war crimes, along with another German jihadist, identified as Farid S., whose wife is on trial in Düsseldorf on charges of delivering 11,000 euros and camera equipment to her husband in Syria.
Robert Rigney, a Berlin-born American who said he had spent almost 15 years here, teaching and writing about immigrant communities, said he had come across Mr. Cuspert in Berlin’s Kreuzberg district around 2009.
“Everyone in Berlin knows this guy,” he said, alluding to immigrant neighborhoods and the high school dropouts, and rap fans, he teaches. “I don’t know what happened to him.”