The United States blacklisted two Greek extremists Tuesday amid a row over Greece's new law which could lead to the early release of a bombmaker from a radical group accused of killing Americans.

Christodoulos Xiros, a convicted hitman for the notorious November 17 underground group, and Nikolaos Maziotis, the leader of the Revolutionary Struggle blamed for a 2007 rocket propelled grenade attack on the US embassy in Athens, were both slapped with terrorist designations by the State Department.