The Obama administration on Monday designated a key rebel group battling Syrian President Bashar Assad's regime as a terrorist organization.

The designation, signed by Secretary of State Hillary Clinton Hillary Diane Rodham ClintonHillary Clinton after debate: 'Everyone better vote' Hillary Clinton: 'Black Lives Matter' is 'very profoundly a theological statement' House in near-unanimous vote affirms peaceful transfer of power MORE, targets Syria's Jabhat al-Nusra and other groups linked to al Qaeda in Iraq, which was tabbed a terrorist organization in 2004. The move will be formally announced in Tuesday's Federal Register.

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The decision, widely seen as an effort to organize the Syrian opposition along lines that are acceptable to the United States, comes as Clinton heads to Morocco on Wednesday for a U.S.-backed Friends of Syria meeting.

The secretary is expected to recognize a newly formed Syrian National Alliance, which excludes al Nusra, as the legitimate representative of the Syrian people, following the lead of France, Britain, Turkey and several Gulf states

"She'll want to hear from [the Syrian opposition], both in her own meeting and in the broader meeting about how they see things going forward both in terms of their own internal organization about their connectivity with Syrians inside Syria about their transitional planning about the needs that they see for external support, how they would have us best direct the nonlethal support and humanitarian support that we are providing," State Department spokeswoman Victoria Nuland said Monday. "So she'll want to hear about all of those things, but, you know, she's been clear that we'd like to offer them more support and I think you'll see some of that at Marrakech on Wednesday."

U.S. officials have expressed concern that radical Islamists with ties to al Qaeda are gaining traction in Syria as Assad appears to be increasingly losing control of the country after a 20-month civil war. Some critics of President Obama's foreign policy have argued for a more forceful U.S. intervention in the war in order to prevent Islamists from taking over.

The designation bans U.S. residents from providing material support for al Nusra, including financial assistance, training or advice.