US Secretary of State John Kerry will hold a meeting Wednesday with Afghan President Hamid Karzai and the head of Pakistan's armed forces, Ashfaq Kayani, a US diplomatic source said.
Kerry, in Brussels for a gathering of NATO foreign ministers on Tuesday, "has offered to host a meeting with Afghan and Pakistani officials", the source said.
Along with Karzai and Kayani will be Afghan Defence Minister Bishmullah Mohammadi and Pakistan Foreign Secretary Jalil Abbas Jilani, the source added.
The meeting, which was not originally on Kerry's agenda, is part of a series between the three parties, the source said, with neighbouring Pakistan a key player as NATO forces prepare to withdraw from Afghanistan in 2014.
Afghanistan is high on the agenda for Tuesday's NATO meeting, Kerry's first as US secretary of state, as the alliance prepares to hand over security duties to the Afghan national army.
Relations between Islamabad and Kabul have been strained for many years, with Karzai charging Pakistan with aiding and abetting the Taliban rebels who seek refuge along their rugged border.