"U.S. Suspects More Direct Threats Beyond ISIS" By Sam Schaffer

"In terms of threat to the homeland, Khorasan may pose as much of a danger as the Islamic State," director of national intelligence James R. Clapper said Wednesday.

Shortly after the United States began what potentially could be a lengthy military campaign targeting the Islamic State, intelligence and law enforcement officials (most notably Mr. Clapper) acknowledged a group that could pose a more direct threat to America and the West.
The group, called Khorasan, appeared last year as a Syrian cell with intentions to attack America or its installations overseas. It is led by Muhsin Al-Fadhli, a former Al-Qaeda officer who was part of Osama Bin Laden's inner circle; a small group of men and possibly one of the only groups who had knowledge of the 9/11 attacks beforehand. 
Along with other Al-Qaeda splinter groups such as the Nusra Front, Khorasan has been suppressed by the rise of the Islamic State, and will probably seek to fill the vacuum left once ISIS has been defeated. In addition, this organization is more interesting in attacking the West than it is in carving out territory in Syria and Iraq. Whereas ISIS simply wants to be left alone by the US, Khorasan prefers to propagate terror rather than act as a organized militant group. 
Even though the U.S. has anknowledged them as a direct threat, there is little to no knowledge on the group, their size and scope, and potential terror plots that could be enacted in the US, or any of its allies or installations overseas. 

Khorasan and the Nusra Front are only two of multiple rebel groups (that have been defined terrorist organizations) that exist within the borders of Syria and Iraq. The number of groups has led to friction, and in some cases infighting between groups with differing idealogies. Although this may seem like it would lead to the collapse of jihadist groups in the region, it will only lead to the dominance of another. This group presents a pressing issue that must be tended to at once.