The military in Pakistan has confirmed that a senior Afghan Taliban commander, Mullah Abdul Ghani Baradar, was captured last week in Karachi.
News of the arrest was first reported in Washington but until now Pakistan refused to confirm it officially.
The military says the delay in confirmation was due to detailed identification procedures.
US officials said on Tuesday that US and Pakistani agents seized Mullah Baradar in Karachi on 8 February.
Pakistan's Foreign Minister, Shah Mehmood Qureshi, told the BBC that Mullah Baradar was being questioned. He gave no other details.
The prisoner was second to Taliban founder Mullah Omar and believed to have been responsible for the southern Helmand province.