US air strikes in Afghanistan this year have already significantly surpassed the total number conducted in 2015.
US warplanes have conducted around 700 air strikes so far this year, compared to about 500 in total last year, according to US military officials.
Ending US involvement in Afghanistan was one of President Barack Obama's signature promises and he declared the combat mission over at the end of 2014.
In the last year of his presidency, however, rising violence has led Mr Obama to keep more US forces in the fight, both to target a growing presence from the so-called Islamic State militant group, and back up struggling Afghan troops.
Top US military commanders in Afghanistan successfully pressed Obama to reverse earlier restrictions on the use of airstrikes, clearing the way for a spike in attacks on Islamic State and Taliban targets.
"The increase in strikes is due to the additional authorities US forces received and due to the Afghan change in strategy to offensive operations," US military spokesman Brigadier General Charles Cleveland said in a statement.
"The new authorities have allowed the US to be more proactive and deliberate in supporting this year's Afghan offensive operations and in aggressively targeting [IS]."
With no end in sight for one of the US's longest wars, any decisions on the future of the airstrikes and nearly 9,000 US troops that will remain in Afghanistan will be up to the winner of the 8 November presidential election.
Of the approximately 700 air strikes that occurred between 1 January and 20 October, about 240 were under rules approved by Mr Obama in June that allowed US forces to more actively support Afghan troops during strategic combat operations, Brig Gen Cleveland said.
A similar number were conducted against "counter terrorism" targets, including about 50 against al-Qaeda and 190 against Islamic State, he said.
Other air strikes can be conducted in defence of US and international military advisors, as well as some Afghan troops.
US air strikes have been credited with helping to prevent Taliban forces from completely overrunning cities like Lashkar Gah, the capital of embattled Helmand province, but militants still contest or control as much as a third of the country.
"Washington's military planners originally expected Afghan troops to be able to hold their own more than a decade after the United States' initial invasion," the private intelligence firm Stratfor concluded in a recent report.
"But with instability still plaguing Afghanistan's north, south and east, they are as dependent on foreign air power and aid as they were when Operation Enduring Freedom began."
The Afghan air force has also nearly doubled its airstrikes, US officials said, but has yet to fully take over the air war against Taliban and other insurgents.
"[US] air strikes are very important and we need them for a longer time to tackle our enemies," Afghan Ministry of Defense spokesman Dawlat Waziri said.
In Afghanistan, the US Air Force maintains a single squadron of F-16 fighter bombers, a unit of armed unmanned aircraft, and a handful of special operations AC-130 gunships.
The US army also deploys its own Apache attack helicopters, and have been observed supporting Afghan troops in places like Kunduz.
