The document was leaked in spectacularly bad timing for the one-day visit, which had been aimed at warming frosty ties between the two neighbours, blighted by mutual accusations over the violence in both countries.[break]
The report -- seen by The Times newspaper and the BBC -- was compiled from information gleaned from insurgent detainees and was given to NATO commanders in Afghanistan last month, the media reports said.
The "State of the Taliban" document claims that Islamabad, via Pakistan´s ISI intelligence agency, is "intimately involved" with the insurgency and that the Taliban assume victory is inevitable once Western troops leave in 2014.
The BBC said the report was based on material from 27,000 interrogations of more than 4,000 captured Taliban and Al-Qaeda operatives.
"Pakistan´s manipulation of the Taliban senior leadership continues unabatedly," the report was quoted as saying.
In Kabul, Afghan foreign ministry spokesman Janan Mosazai told reporters before the story broke that Khar´s visit aimed to open a "new phase" in cooperation between the two countries.
Kabul, which has long accused Islamabad of supporting the 10-year insurgency in Afghanistan, put relations on ice after the September murder of its peace envoy Burhanuddin Rabbani, which one Afghan minister blamed on Pakistani spies.
Kabul said the bomber who killed Rabbani was a Pakistani and accused the Pakistani government of hindering the investigation.
"After the death of Rabbani we boycotted some of the bilateral and trilateral meetings (including the US) with Pakistan," a senior official in Karzai´s office told AFP.
"This visit is aimed at improving our relations as well as at resuming those meetings."
In December, Pakistan boycotted the Bonn conference on the future of Afghanistan to protest against US air strikes that killed 24 Pakistani soldiers along the porous Afghan border on November 26.
Khar meets her Afghan counterpart Zalmai Rasoul and Karzai amid tentative moves towards negotiations in Qatar between Washington and the Taliban, who were ousted from power by the 2001 US-led invasion.
Karzai has given his blessing to the Taliban opening a political office in the Gulf state, but is wary of being sidelined and has insisted that his government has a central role in any peace talks.
In Islamabad, foreign ministry spokesman Abdul Basit said Khar´s talks would cover "the security situation in Afghanistan and the reconciliation process".
"We hope the visit would further enhance mutual understanding on major issues and bring the two countries closer," he told AFP.
Pakistani analyst Rahimullah Yusufzai said Khar´s trip was important because it is her first to Afghanistan and comes after a gap in Pakistani official visits to Kabul.
He said both governments "feel a bit left out" of the Qatar negotiations and "would be trying at least to find out what is happening and maybe try to coordinate their own policies accordingly".
But he said many problems between the two countries remain unresolved, including the Rabbani assassination, adding: "I don´t expect any real breakthrough at these talks."
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