The Taliban announced on Wednesday that it was kicking off its annual spring offensive in Afghanistan, which marks the start of the so-called fighting season.
Operation Al Khandaq will target US forces and "their intelligence agents" as well as their "internal supporters", a Taliban statement said.
Al Khandaq will mainly focus on "crushing, killing and capturing American invaders and their supporters", it added.
It stated the presence of American bases "sabotages all chances of peace" and were key to "prolonging the ongoing war", which began with the US-led intervention in 2001 that overthrew the Taliban regime.
The group said the offensive was partly a response to US President Donald Trump's new strategy for Afghanistan announced last August, which gave US forces more leeway to go after insurgents.
The onset of spring has traditionally brought an uptick in violence in Afghanistan, as melting snows allow fighters to more easily traverse the mountainous terrain, but this year the Taliban has carried out attacks throughout the winter.
It launched a series of devastating attacks in the Afghan capital Kabul, killing and wounding hundreds of civilians.
Defense ministry spokesman Mohammad Radmanish dismissed the Taliban announcement as "propaganda".
The Taliban has been under pressure to accept Afghan President Ashraf Ghani's February offer of peace talks, but the statement made no mention of the proposal.
Western and Afghan experts said its announcement was an apparent rejection of the offer and heralded more intense fighting in the drawn-out war.
"We're in for a hot and busy summer," a foreign diplomat in Kabul told AFP.
Afghan political analyst Ahmad Saeedi said the Taliban appeared to consider America's rejection of the group's own request for direct peace talks with the US in February as leaving them with "no other choice but to fight".
"This year they will try to weaken the (Afghan) government even further. They will try to derail the election process," the Kabul University professor told AFP. "A weak government would eventually mean forcing the US to talk to them."
The US-backed Afghan government is under pressure on multiple fronts this year as it prepares to hold long-delayed legislative elections even as its security forces struggle to get the upper hand on the battlefield and prevent civilian casualties.
On Sunday, a suicide bomber blew himself up in a crowd outside a voter registration center in Kabul, killing 60 people and wounding 129, according to the latest figures from the health ministry.
The ISIS group claimed responsibility for the bomb, but Western and Afghan officials suspect it receives assistance from other organizations, including the Taliban's Haqqani Network, to carry out attacks.
Officials on Tuesday announced that 11 Afghan soldiers were killed in a series of Taliban attacks across the country.
At least five soldiers were killed when their checkpoint was attacked by the Taliban in western Farah province, according to Mohammad Naser Mehri, the provincial governor's spokesman.
Two soldiers were wounded in that attack, in the Bala Buluk district. Mehri said six Taliban fighters were killed and three others were wounded in the battle, which lasted several hours.
In the eastern Ghazni province, insurgents killed at least four members of the local police force and wounded seven.
The Taliban there targeted the local police security post in the province's district of Jaghatu, said Arif Noori, spokesman for the provincial governor. He also said the gunbattle lasted several hours and that the Taliban used artillery and rocket-propelled grenade launchers.
Later Tuesday, two policemen were killed and six soldiers were captured in attacks on their checkpoints in western Badghis province, said Mohammad Naser Nazari, a member of the provincial council.
