NATO would however not enter Pakistan to hunt down militants based there, Secretary General Jaap de Hoop Scheffer told reporters.

Scheffer was visiting amid high tension between Afghanistan and Pakistan over a spate of violence, including the bombing of the Indian embassy here this month that Kabul has directly blamed on its neighbour's intelligence agency.

"The bottom line is that the present situation cannot be acceptable for anyone," Scheffer told reporters after talks with President Hamid Karzai.

"Our forces in Afghanistan are also the victims of the surge and uptick in violent incidents we have seen recently. But let us practise a regional approach and let us involve all the regional actors here," he said.

Afghan and Western officials have long said that the Taliban and Al-Qaeda have been able to regroup in Pakistan's semi-autonomous tribal areas after they were expelled from Afghanistan in 2001 in a US-led invasion.

Some accuse Islamabad of not doing enough to tackle them and criticise its efforts to negotiate peace deals.

"Only saying Pakistan is part of the problem or Pakistan is the problem might clear your conscience, but will not help in solving the problem," Scheffer said, likely referring to Kabul's crossborder fingerpointing.

"But my preferred option is Pakistan is part of the solution," he said.

There are fears in Pakistan that international forces will launch "hot pursuit" raids into its tribal belt as attacks soar in Afghanistan.

Islamabad has warned it would not allow this to happen and insists it is dealing with the problem in its own way.

Scheffer said ISAF's UN mandate barred it from entering Pakistan.

"It is crystal clear that if NATO forces are shot at from the other side of the border, there is always the right of self-defence.

"But you will not, I repeat not, see NATO forces crossing into Pakistani territory and you will not see the alliance seeking another UN mandate."

ISAF, which includes about 53,000 soldiers from 40 nations, works alongside Afghan forces and a US-led coalition of about 14,000 soldiers to battle the insurgents.