The US is under pressure to explain why Secretary of State Mike Pompeo referred to the Afghan Taliban as terrorists, as peace talks with the group continue.
Mr Pompeo was speaking to a group of students in Des Moines, Iowa, on Monday when he said he had a team on the ground “trying to negotiate with the Taliban terrorists in Afghanistan”.
The Taliban has not been declared a terrorist organisation by the US.
US State Department spokesman Robert Palladino refused to elaborate on Mr Pompeo’s comments.
"The secretary’s words speak for themselves and I am not going to go beyond that," Mr Palladino said.
US and Taliban representatives have been in talks in Doha, Qatar, for several days attempting to finalise a draft agreement to end the 17-year war and potentially begin withdrawing the 14,000 US troops still deployed in Afghanistan.
Mr Palladino said the peace talks were making progress but there was more work be done to reach an agreement.
"These discussions are ongoing and what we're focusing on are the four interconnected issues that are going to compose any future agreement," Mr Palladino said. The four issues are have been defined as terrorism, troop withdrawal, intra-Afghan dialogue and ceasefire.
Meanwhile at least 16 people were killed in a suicide attack on a construction company near the airport in the Afghan city of Jalalabad. Five alleged attackers were killed by security forces.
A clearance operation was ongoing on Wednesday afternoon, with security defusing two suicide vests, a car bomb, and multiple mines planted by the attackers.
"Armed suicide bombers attacked and managed to enter the building of a private construction company early this morning," said Nangarhar Provincial council member Zabihullah Zmarai. "A number of civilian workers of the company have been killed."
No group has claimed responsibility for the attack, but both ISIS and the Taliban are active in Nangarhar province.
Analysts have warned that the Taliban is likely to ramp up attacks as they try to get leverage at the negotiating table.
Last week at least 23 security forces were killed in a major assault on a joint US-Afghan base in Helmand province.
