WASHINGTON -- Dozens of seasoned militant fighters, including some mid-level planners, have traveled to Syria from Pakistan in recent months in what U.S. intelligence and counterterrorism officials fear is an effort to lay the foundation for future strikes against Europe and the United States.
"We are concerned about the use of Syrian territory by the al-Qaida organization to recruit individuals and develop the capability to be able not just to carry out attacks inside of Syria, but also to use Syria as a launching pad," CIA director John Brennan told a House panel recently.
The extremists who concern Mr. Brennan are part of a group of al-Qaida operatives in Pakistan that has been severely depleted in recent years by a decade of U.S. drone strikes. But the fighters still bring a wide range of skills to the battlefield, such as bomb-building, small-arms tactics, logistics, religious indoctrination and planning, though they are not believed to have experience in launching attacks in the West.
Syria is an appealing base for these operatives because it offers them the relative sanctuary of extremist-held havens -- away from drone strikes in Afghanistan and Pakistan -- as well as ready access to about 1,200 American and European Muslims who have gone there to fight and could be potential recruits to carry out attacks when they return home. Senior counterterrorism officials have voiced fears in recent months that these Western fighters could be radicalized by the country's civil war.
New classified intelligence assessments based on information from electronic intercepts, informers and social media posts conclude that al-Qaida's senior leadership in Pakistan, including Ayman al-Zawahri, is developing a much more systematic, long-term plan than was previously known to create specific cells in Syria that would identify, recruit and train these Westerners.
In the past, al-Qaida has blessed the creation of local branches in places like Yemen, where an affiliate has tried to strike the United States. But the effort in Syria would signify the first time that senior al-Qaida leaders had set up a wing of their own outside Pakistan dedicated to conducting attacks against the West, counterterrorism officials said. It also has the potential to rejuvenate al-Qaida's central command, which President Barack Obama has described as being greatly diminished.
The assessment by the United States, however, has some detractors among even its staunchest counterterrorism partners, which also see an increase in Pakistan-based veterans of al-Qaida among Syrian rebel groups but disagree over whether they are involved in a coordinated plan to attack the West.
"At this stage, it's a lot less organized than a directed plan," said one Western security official. "Some fighters are going to Syria, but they're going on an ad hoc basis, not at an organized level."
Most of the operatives identified by intelligence officials are now focused on attacking Syrian government troops and occasionally rival rebel factions. But the fact that these kinds of operatives are showing up in Syria indicates to U.S. officials that Mr. Zawahri is also playing a long game -- counting on easy access to Iraq and al-Qaida support networks there, as well as on the United States' reluctance to carry out drone strikes or other military operations against targets in Syria.
"A key question, however, is how using Syria as a launching pad to strike the West fits into Zawahri's overall strategy, and if he's soft-pedaling now, hoping to consolidate al-Qaida's position for the future," said one U.S. counterterrorism official. "Clearly, there is going to be push and pull between local operatives and al-Qaida central on attack planning. How fast the pendulum will swing toward trying something isn't clear right now."
The new assessment is not likely to change U.S. policy toward Syria anytime soon, but it puts pressure on the Obama administration and its allies because it raises the possibility that Syria could become the next Afghanistan.
The al-Qaida veterans have multiple missions and motivations, counterterrorism officials say. Like thousands of other foreign fighters, many have been drawn on their own to Syria to fight the government of President Bashar Assad.
Many others, like Abu Khalid al-Suri, a Syrian-born veteran of al-Qaida, were sent by the terrorist group's central command in Pakistan first to fight Mr. Assad, but also to begin laying the groundwork to use enclaves in Syria to launch attacks against the West, U.S. officials said.
Mr. Suri, who is believed to have been close to Osama bin Laden and to have fought against U.S. forces in Afghanistan and Iraq, was sent to mediate conflicts between al-Qaida's main affiliate in Syria, the Nusra Front, and another extremist faction, the Islamic State of Iraq and the Levant, which al-Qaida has disavowed. He was killed in a suicide attack in February by the rival group.
Many of the al-Qaida planners and operatives from Afghanistan and Pakistan have clustered in the east and northwest sections of Syria, in territory controlled or heavily influenced by the Nusra Front, intelligence officials said.