BBC: Afghan President Hamid Karzai has threatened to send troops over the border into Pakistan to confront militants based there.
He said that when militants crossed over from Pakistan to kill Afghans and coalition troops, his nation had the right to retaliate in "self-defence".
Mr Karzai's remarks came two days after Taleban fighters attacked an Afghan jail, freeing hundreds of prisoners.
Pakistan warned it would not tolerate outside interference in its affairs.
Yusuf Raza Gilani, Pakistan's prime minister, said the border between their two countries was too long to police.
Destabilise
"Neither do we interfere in anyone else's matters, nor will we allow anyone to interfere in our territorial limits and our affairs," he told the Associated Press news agency.
"We want a stable Afghanistan. It is in our interest. How can we go to destabilise our brotherly country?" Karzai Issues Warning to Pakistan >>> | June 15, 2008
The Dawning of a New Dark Age (Paperback - UK)
The Dawning of a New Dark Age (Hardback - UK)
