Afghan President Ashraf Ghani on Thursday announced the first unconditional ceasefire with the Taliban, coinciding with the end of the Muslim fasting month. But that excludes other militant groups such as Islamic State.
The group has developed a stronghold in Nangarhar, on the porous eastern border with Pakistan, and become some of the country's most dangerous militants since they appeared around the start of 2015.
"(Operations against ISIS) will continue, in fact will be even intensified during this period of ceasefire as we focus on ISIS," U.S. Army General John Nicholson, commander of U.S. and international forces in Afghanistan, told reporters.
Nicholson said the ceasefire could free resources for operations against Islamic State, but some would remain to monitor the Taliban and for force protection.
"We're going to leave resources devoted to protecting our forces and watching the enemy, even those that participate in the ceasefire, as well as intensifying the pressure on ISIS," Nicholson said.
Afghan commandos, supported by U.S. Special forces and American and Afghan air power, have been carrying out an operation against the militants in Nangarhar.
The ceasefire decision came after a meeting of Islamic clerics this week declared a fatwa, or ruling, against suicide bombings. One such bombing, claimed by Islamic State, killed 14 people at the entrance to the clerics' peace tent in Kabul, Afghanistan's capital.
Nicholson said the ceasefire was "significant" because it was the first of its kind during the 17-year old war. The Taliban has not yet reacted to the announcement.
"I don't know what the Taliban will do," Nicholson acknowledged.
Privately, Western officials have expressed caution.
"I don't think we have a feeling about it," a NATO official, speaking on the condition of anonymity, said when asked if there was optimism about the ceasefire.
Michael Kugelman, with the Wilson Center think tank in Washington, said the ceasefire was largely symbolic.
"We should keep our expectations in check ... If anything, it will make the Taliban even stronger by giving it some breathing room and time to regroup and reload," Kugelman said.