If US troops leave Afghanistan they will be leaving the country open to assault from the Taliban and from Daesh, but their presence is also a sticking point for political resolution, Rifaat Hussain, leading Pakistani security analyst, told Radio Sputnik.
The Taliban has strengthened its presence in Afghanistan since the US withdrew combat troops from the country in 2014, and the deteriorating security situation means that US troops could be there for up to ten years, Hussain said.
"The Americans are very quietly allowing their remaining troops, about 10,000, into a combat support role, and they are using drone attacks and aircraft to try and get the situation under control but it seems likely that Afghanistan will remain vulnerable to instability for the foreseeable future, and hence the Americans will be tempted to prolong their stay in Afghanistan much beyond 2017."
"I would say that American troops are there to stay for a long period of time, maybe up to five or ten years," though the outcome of next year's US elections will also reflect whether the US public is willing to spend the necessary billions to keep a strategic foothold in the region, he said.
The presence of US troops is also having an effect on the "stillborn" Afghan peace process, which is hampered by the Taliban's demand for a definite time frame for the withdrawal of US troops before they come to the negotiating table.
"On the other hand the Afghan unity government does not want the American forces to withdraw because they think that if the Americans were to pack up and leave, the Afghanistan unity government will be more likely to fall prey to the Afghan insurgency, and then Daesh will strengthen its foothold."
"Some of the Afghan Taliban who are fighting the unity government forces are drifting more towards the Daesh element, so this means that Afghanistan will become more vulnerable to a civil war situation."
"If that happens I am not sure that the Afghan army is going to stay as a united force, and more likely that they are going to split and throw their weight behind the winning force."
The US-led NATO combat mission in Afghanistan formally ended in December 2014, and was replaced by the supposedly non-combat "Resolute Support" mission to train Afghan security forces.
However, in October 2015 US President Barack Obama again reversed earlier announcements about the drawdown, and instead announced that almost 10,000 US troops will remain in the country throughout most of 2016.
Cook said the special forces are operating in a "support backup" role for Afghan forces.
"This is a combat situation, but they're not in the lead," the press secretary said.