Pentagon chief Ashton Carter headed to southern Afghanistan on Sunday to review plans to withdraw US forces in a volatile area that has long preoccupied American commanders.
In his first visit abroad days after he took over as US defence secretary, Carter met senior officers and troops at Kandahar airfield, a key base that hosts US special forces and advisers as well as helicopters and other aircraft.
After talks in Kabul with President Ashraf Ghani on Saturday, Carter made clear that President Barack Obama's administration was considering slowing down a planned timetable for a troop pullout. The current plan would reduce the existing force of more than 10,000 to about 5,500 by the end of the year, and then pull out all troops in two years' time - when Obama's term ends.
Under that blueprint, US forces would have to withdraw from Kandahar airfield this year, but Carter suggested the timing of base closures and troop withdrawals could be reviewed.
Kandahar base serves as a jumping off point for special operations forces targeting Al-Qaeda and Taliban figures, as well as for drones and surveillance aircraft.
During a surge of troops in 2010, thousands of US forces poured into Kandahar and Helmand province to try to turn the tide in the war against the Taliban, which was toppled from power after a US-led invasion in 2001.
Carter flew to Kandahar amid intense fighting in neighbouring Helmand, where the Taliban have sought to regain ground lost during the US-led surge of forces in recent years.
Afghan security forces have launched a major counter-offensive near Sangin in the past two weeks in Helmand, involving troops from three army corps and helicopters, US officers said.
The offensive featured about 2,000 Afghan troops and Russian-made helicopters launching air strikes in support of ground forces, officers said. General John Campbell, the US commander in Afghanistan, said the operation was entirely "Afghan-led and Afghan planned" and unprecedented for the Afghan forces in terms of its complexity.
"I'm really happy with what's happening in north Helmand right now," he told reporters Saturday. But he said he could not provide more details as the operation was ongoing. The Taliban reportedly managed to penetrate a major Afghan base in Helmand in November but were repulsed after heavy losses. The former Camp Bastion base was a hub for NATO forces until it was turned over to local forces in October.