Intelligence officials say the U.S. needs to be on the alert for terror threats from a militant group in Syria -- and it's not the Islamic State. While the army also known as ISIS continues to seize land in the region, Khorasan seems to have its sights set on attacking the U.S. 

The Obama administration has repeatedly said ISIS does not present an “immediate threat” to the U.S., but that could soon change. ISIS spokesman Abu Muhammad al-Adnani released a statement Monday urging militants to kill Americans and French citizens around the world.

In the meantime, Khorasan could be the bigger threat of potential attacks on U.S. soil, National Intelligence Director James Clapper said Thursday, according to the New York Times. “In terms of threat to the homeland, Khorasan may pose as much of a danger as the Islamic State,” he said.

What is Khorasan?

Led by Muhsin al-Fadhli, who was thought to have a very close relationship with Osama bin Laden, Khorasan is one of al Qaeda’s affiliates in Syria and possibly one of the most secretive groups operating under the cover of Syria's civil war. Unlike many of the other groups in Syria who seek to overthrow Syrian President Bashar Assad, ISIS or both, Khorasan has expressed little interest in the war's outcome.

Most notably, the group has ties to notorious Yemeni bomb maker Ibrahim al-Asiri, who is part of al Qaeda’s branch there, al Qaeda in the Arabian Peninsula. Asiri is believed to be responsible for making the underwear bomb used by Umar Farouk Abdulmutallab in 2009, the Associated Press reported.

Who is in Khorasan? Where do they come from?

The group’s leader al-Fadhli is believed to be living in Syria. Until recently, the Kuwaiti-born 31-year-old lived in Iran, where he reportedly led al Qaeda’s Iranian branch after the former leader was detained. When former leader Yasin al-Suri was released and resumed his role leading al Qaeda in Iran, Fadhli had to be reassigned, the Long War Journal reported. While there have been no official reports on the matter, it is believed that al Qaeda had to reshuffle personnel and sent Fadhli to Syria.

Intelligence and terrorism experts said the group is made up of al Qaeda members from across the Middle East and Europe. The majority come from Afghanistan, Yemen and Syria, but as the group’s goals suggest, they’ve been able to recruit Europeans and Americans who came to fight with other jihadist groups in Syria.

Why are they called Khorasan?

Khorasan was an ancient province of eastern Persia, which the group aims to recreate. The territory encompasses present-day Afghanistan, eastern Iran, Turkmenistan and Uzbekistan. According to jihadists, this the place where they will defeat their enemies.

Why are they a threat to the United States?

The group was sent to Syria by al Qaeda leader Ayman al-Zawahiri, who saw a prime opportunity to recruit Western passport holders. The attraction is that Westerners can board planes back to their homelands more easily, according to the AP.

The group is reportedly working alongside Jabhat al-Nusra, the official al Qaeda branch in Syria, while procuring bombs from Yemen. The goal in Syria is to find people to detonate the bombs.

Fadhli, the Khorasan leader, "trains them on how to execute terror operations in the Western countries, focusing mostly on means of public transportation such as trains and airplanes," according to the Arab Times.

Relationship with ISIS

Fadhli influenced al Qaeda’s decision to disassociate itself from ISIS in February 2014, according to a report by Long War Journal.

Al Qaeda’s decision to follow Fadhli’s advice about ISIS “indicates the confidence al Qaeda leadership has in al-Fadhli,” according to the Arab Times. “It also confirms that al-Fadhli is the de facto leader of al Qaeda in Syria, even though it has not been officially announced over fear of exposing him.”