In total, they killed 27 hostages and tortured many more.
Majority were captured in Afghanistan following the September 11, 2001 attacks on the United States.
The State Department, in imposing sanctions on Kotey past year, said he likely engaged in executions and torture, including electronic shock and waterboarding, and recruited several British nationals to IS.
Kotey had also acted as a recruiter and was responsible for recruiting several British nationals to join the militant group, the State Department said.
A US -led coalition has pushed Islamic State out of most of the territory it controlled in Iraq and Syria, but its leader, Abu Bakr Al-Baghdadi, who proclaimed the self-styled caliphate in 2014, remains at large.
Kotey and ElSheikh were captured in early January by the US-backed Syrian Democratic Forces, said an American defence official.
U.S. officials were informed in mid-January that the militia might have captured the men, the newspaper reported, adding that the officials later confirmed their identities using fingerprints and other biometric measurements. Elsheikh was known for "waterboarding, mock executions, and crucifixions" of hostages. Cmdr. Sarah Higgins of the Navy, a Pentagon spokeswoman for detention policy issues, declined to comment.
Russian pilot 'killed in fighting' after plane downed in Syria
The Russian Defense Ministry confirmed the downing of the Su-25 and said the pilot was killed in fighting with "terrorists". But Idlib remains under militant control, and HTS exercises significant influence even over areas it does not formally hold.
North Korea earned $200mn from banned exports, arms-sale
These range from banning coal, iron, lead, textiles and seafood to capping crude-oil and refined petroleum products' imports. However, Syrian officials told the monitors that the only North Korean experts on its territory were involved in sports.