The State Department has designated Syria's al-Nusra Front — a highly effective jihadist Syrian rebel group — as a Global Terrorist organization because of its direct links to al-Qaeda in Iraq (AQI), Karen DeYoung of The Washington Post reports.

The designation prohibits Americans from having any financial dealings with the group — which makes up about nine percent of rebel forces — and freezes any of its assets under U.S. control.

The move is part of a U.S. effort at isolating extremist groups while promoting the newly recognized Syrian National Coalition so that post-Assad Syria doesn't turn into a free-for-all.

But challenges remain since U.S.-made weapons have gone to hardline jihadists who have turned out to be the opposition's most organized and best fighters in the 21-month civil war.

The al-Nusra front has been leading rebel attacks from the front lines, including the recent capture of the only significant government facility remaining west of Aleppo.

Over the weekend The New York Times detailed the group's extensive ties to al-Qaeda in Iraq (AQI), which help found al-Nusra Front and provides it with money, expertise and fighters. One former member of AQI told the Times that many members of the group were fighting with al-Nusra in Syria.

“They are well trained mentally and militarily,” Major Issawi, the official in Anbar, told the Times. “They are so excited about the fighting in Syria. They see Syria as a dream coming true.”

Several dozen FSA in Damascus announced they that they had joined al-Nusra because of their fighting prowess. But others are very wary of the group and their Islamic ambitions, especially in the "liberated" northern areas where secular and jihadist rebel groups remove the safety on their guns as they pass each other's military bases.

“After the fall of Bashar there will be so many battles between these groups,” an Iraqi who joined the regular Free Syrian Army told the Times. “All the groups will unite against al-Nusra. They are like a snake that is spreading its poison.”

The extremists agree since the group says it will fight any secular government after Assad because it aims to create an Islamic state in Syria ruled by strict Sunni Islam.

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