Al-Qaida plots comeback in Afghanistan: US

But without the agreement that would authorize international forces to stay in Afghanistan, President Barack Obama has threatened to pull all troops out, and Nato forces would follow suit.

After talking to Afghan President Hamid Karzai this week, Obama ordered the Pentagon to begin planning for the so-called zero option.

US military and intelligence officials say unless they can continue to fly drones and jets from at least one air base in Afghanistan — either Bagram in the north or Jalalabad in the east — al-Qahtani and his followers could eventually plan new attacks against US targets, although experts do not consider him one of the most dangerous al-Qaida leaders.

The officials spoke on condition of anonymity because they were not authorized to discuss publicly the secret counterterrorism campaign or intelligence.

Administration officials have hoped that the US could eventually wind down counterterrorism operations like drone strikes in the region after reducing the al-Qaida network, leaving local forces in Afghanistan and Pakistan to control the remnants.

But al-Qaida is not weakened enough yet, and US officials have testified that the inexperienced Afghan forces aren't ready to take over the task unaided.

National Security Council spokeswoman Caitlin Hayden this week said that "as the possibility of a full withdrawal has grown in Afghanistan", the administration was "undertaking a methodical review of any US capabilities that may be affected and developing strategies to mitigate impacts".