There are growing indications that supporters of both the al-Qaida and Islamic State terror groups have their sights set on Afghanistan, emboldened by the Taliban takeover of the country late last month.
Initial reports over the past week or so have highlighted an uptick in chatter among terrorists, expressing a desire to go to Afghanistan, but a top U.S. intelligence official said Tuesday that some already have begun the journey.
"We are already beginning to see some of the indications of some potential movement of al-Qaida to Afghanistan," Central Intelligence Agency Deputy Director David Cohen said during a panel discussion at an intelligence summit outside of Washington.
"But it's early days," he said, warning that al-Qaida could reconstitute in as little as a year. "We will obviously keep a very close eye on that."
U.S. intelligence officials declined to share specifics on the identities of the al-Qaida members making their way back to Afghanistan, or about where they were coming from, though a recent video posted online showed Amin al-Haq, who served with al-Qaida founder Osama bin Laden during the battle of Tora Bora, returning to his native Nangarhar province.
There also have been lingering doubts from other intelligence agencies that some key al-Qaida leaders currently in Iran, like Saif al-Adel, the group's second-in-command, will head back to Afghanistan given they have stronger connections elsewhere.
Still, the CIA warning follows concerns from international counterterrorism officials and analysts about Afghanistan reemerging as a terrorist safe haven.
"There is definitely a very strong sort of sense of enthusiasm out there for Afghanistan," he added.
Analysts, like Charles Lister at the Washington-based Middle East Institute, also have raised concerns, noting growing interest in Afghanistan from supporters of al-Qaida's main rival, the Islamic State (IS).
When asked about the threat, U.S. officials who spoke to VOA last week on the condition of anonymity to discuss intelligence, admitted there was reason for concern. And even before the U.S. completed its withdrawal from Afghanistan, U.S. intelligence agencies were warning of a "trickle" of incoming foreign fighters.
Complicating matters for the U.S. and its allies is the newfound lack of visibility into developments on the ground due to the withdrawal.
"Our current capability in Afghanistan is not what it was six months ago or a year ago," said the CIA's Cohen, though he cautioned it was not an unsurmountable obstacle.
"We with the agency and with our partners have experience in collecting intelligence in in areas that are non-permissive and doing so without a physical presence on the ground," he said. "We will be using many of those same techniques in Afghanistan as we work from over-the-horizon principally, although I think we will also look for ways to work from within the horizon to the extent that is possible."
So far, the intelligence suggests both al-Qaida and IS-Khorasan are well on their way to reestablishing their capabilities.
"The current assessment, probably conservatively, is one to two years for al-Qaida to build some capability to at least threaten the homeland," said Defense Intelligence Agency Director Lieutenant General Scott Berrier.
Other Western counterterrorism officials and aid workers in the region have warned that while al-Qaida is likely to keep a low profile for the foreseeable future, IS-Khorasan has for months been building up its infrastructure in Afghanistan and in neighboring countries.