US forces have captured a senior Pakistan Taliban commander, Latif Mehsud, the state department has said.
The US gave no details of the operation, but Afghan officials said he was seized in eastern Afghanistan and taken to the Bagram base near Kabul.
He was reportedly returning from talks over a mooted prisoner-swap deal, and the capture is said to have angered Afghan President Hamid Karzai.
The US described Latif Mehsud as a “terrorist leader”.
State department spokeswoman Marie Harf said he was a close confidante of the Pakistani Taliban leader, Hakimullah Mehsud.
The group has killed thousands in its conflict with the Pakistani government.
It has also been blamed for the attempted bombing of Times Square in New York in 2010, as well as attacks on US diplomats in Pakistan and many Pakistani civilians.
The group “had also vowed to attack the US homeland again,” Ms Harf said.
Afghan officials were quoted as saying that Latif Mehsud, who is not related to Hakimullah, was taken in Afghanistan’s eastern Logar province last week.
The Pakistani Taliban said he was taken at a Pakistan-Afghan border crossing in Khost province.
Latif Mehsud was reportedly returning from a meeting with Afghan intelligence officers to discuss swapping prisoners.
US and Pakistani media reports said the Afghans were trying to recruit him as a go-between for peace talks.
A spokesman for President Hamid Karzai, Aimal Faizi, told the Washington Post: “The Americans forcibly removed him and took him to Bagram.”
Mr Faizi said Latif Mehsud had only agreed to meet Afghan operatives after months of negotiations.
Some reports say Mr Karzai, who is currently holding talks with visiting US Secretary of State John Kerry, was furious about the US operation.
Latif Mehsud is thought to have started as a driver for a militia leader, but rapidly rose through the ranks.
He had recently become the right-hand man of Hakimullah Mehsud, acting as a negotiator for him in talks with other militia leaders, Pakistani media reports said.
This week, Hakimullah Mehsud told the BBC he was open to “serious talks” with Pakistan’s government but said he had not yet been approached.
In a rare interview, Hakimullah Mehsud denied carrying out recent deadly attacks in public places but said he would continue to target “America and its friends”.
The chief loosely controls more than 30 militant groups in Pakistan’s tribal areas.
After being elected prime minister in May, Nawaz Sharif announced he would open unconditional talks with the Taliban.
The group controls areas in the north-west, and has been blamed for a wave of suicide bombings and other attacks.
Along with Pakistan, the Afghan government has also made overtures for peace with the Taliban. A number of Taliban prisoners have been freed to smooth the process.
US attempts in June to talk to the Taliban, including the opening of a now-shut Taliban office in Qatar, infuriated Mr Karzai.