Babar Ahmad admitted providing support to terrorists at a federal court hearing in New Haven, Connecticut.
He now faces up to 25 years in prison, when he is sentenced in March, Sky News reports.
According to the report, another man, Syed Talha Ahsan, is also expected to change his plea.
The pair was to have faced trial after denying charges of providing material support to terrorists.
Ahmad, 39, and Ahsan, 34, were accused of running websites that sought to raise money, recruit fighters and seek equipment for terrorists in Afghanistan and Chechnya, the report said.
US prosecutors said the two men operated a network of Internet sites known as Azzam publications that attracted worldwide support to the jihadist cause, it added.
--ANI (Posted on 11-12-2013)