The assessment of al Qaeda's efforts in Libya come in response to a report by CNN television that experienced militants from the network - including a former British terror suspect - had been dispatched to the country and had managed to mobilise fighters.
US officials confirmed that al Qaeda had sent some members to Libya and was pushing its north African branch, al Qaeda in the Islamic Maghreb (ADAM), to promote Islamist extremism, but the practical effect remained unclear.
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"Al Qaeda has sent some operatives, and is encouraging local affiliates - namely ADAM - to infiltrate Libya in an attempt to drum up extremist activities," one American official, who spoke on condition of anonymity, told AFP.
But the official said al Qaeda was badly damaged by a decade-long US campaign and that the extremist network found itself marginalised by a wave of popular uprisings in Libya and across the Arab world.
"When it comes to the overthrow of Gaddafi, and the Arab Spring in general, Al Qaeda is arriving late to the game," the official said in an email.
"It shouldn't be a surprise that an organisation so close to strategic defeat would seek opportunities to rehabilitate its image and be relevant again.
"But this is a threat we are well aware of and are working with Libyan authorities to counter."
According to CNN, al Qaeda chief Ayman al-Zawahiri personally ordered a seasoned operative - a former British detainee - to Libya, the television news channel reported citing a Libyan source briefed by Western officials.
The operative, who arrived in Libya in May, has allegedly recruited some 200 fighters in the country's east and Western intelligence agencies are tracking his efforts, CNN said.
Another operative, with European and Libyan passports, was arrested en route to Libya from the Afghanistan-Pakistan region in "an unnamed country," according to CNN.
US officials, however, could not confirm Zawahiri's role or the estimated number of fighters recruited.
