Afghanistan issued harsh words against neighboring Pakistan on Tuesday, accusing it of refusing to help investigate the assassination of former Afghan President Burhanuddin Rabbani and alleging that Pakistani intelligence officials had advance knowledge of the plot.
Afghanistan and Pakistan have long been uneasy allies against the Taliban insurgency, and relations have become increasingly strained since the death of Rabbani, who was appointed by the government to try to broker peace with the Taliban.
If Pakistan does not help, Afghanistan will appeal to the United Nations to get involved, said a spokesman for the government commission investigating the assassination who goes by the single name of Dr. Zia.
Pakistan's government said it was cooperating and denied involvement in the Sept. 20 killing, which dealt a severe setback to efforts to negotiate a political solution with the Taliban after 10 years of war.
"Prime Minister (Reza Yousuf) Gilani had offered cooperation in the investigation into professor Rabbani's assassination during his visit to Kabul," said Pakistani Foreign Ministry spokeswoman Tehmina Janjua. "Pakistan stands by this commitment."
The assassin gained entry to Rabbani's home by claiming to be a peace emissary from the Taliban's governing council, which is based in Pakistan. As he neared Rabbani he detonated explosives that were hidden inside his turban.
The Taliban has not claimed responsibility for Rabbani's death.
Speaking to reporters, Zia said the sophistication of the bomb hidden in the attacker's turban pointed to a link with Pakistan.
He said the commission was also basing its accusations of Pakistani involvement on the confession of the suspected mastermind, Hamidullah Akundzadeh, an Afghan who was arrested 18 hours after Rabbani was assassinated.
"Why are we claiming Pakistan government is behind this attack? Because the explosive that was in that hat was not the idea" of a few Taliban leaders, said Zia, who is also deputy chief of the Afghan intelligence service. "It was a very sophisticated device inside that hat."
He said the Pakistani government delivered a message through its embassy Tuesday informing "us that they are not ready to cooperate with us."
He added that their explanation suggested Pakistan was upset with remarks about the case that Afghan officials had made to the media.
"Now we have to go to the U.N. for help," he said.
At the Kabul news conference, the commission gave reporters a 20-minute digital video of Akundzadeh's alleged confession. He talks of meeting members of the peace council in Kabul and then returning to Quetta, Pakistan, to brief Taliban leaders based there on the conversations.
Later, he accompanied the bomber, a Pakistani man named Esmatullah, on a bus trip back to Kabul, stopping along the way to stay at the home of Akundzadeh's relatives in Kandahar.
Afghan authorities might have been close behind at one point, because they arrested two relatives who hosted Akundzadeh and the bomber, the suspect said.
Once in Kabul, the two men parted ways, and Akundzadeh said he learned of the attack on Rabbani in a phone call from a friend.
Zia stopped short of directly accusing Pakistani intelligence authorities of being behind the explosive device, but Afghan Interior Minister Bismullah Khan Mohammadi said Oct. 1 in an Afghan parliamentary session that the ISI was involved in the killing.
Zia said the Afghan government has arrested suspects but that other Afghans are hiding in Quetta.
"We want them arrested and handed over to us. We have all their photos, home addresses and even their contact numbers. Our requests (to Pakistan) are very clear, but they are not helping us."
Zia said that according to Akundzadeh's confession, the plan to assassinate Rabbani was hatched six months ago and that he was targeted for being both a high-ranking official and the head of the peace council. He alleged that the Pakistani agency knew about the attack, which he said also had the involvement of the Taliban's Quetta-based leadership council.
"They have the full support of the Pakistan government," he said.
Pakistan has denied the allegation and has argued that the evidence the Afghans have given to Pakistan consisted solely of the confession of Akundzadeh.
"Instead of making such irresponsible statements, those in positions of authority in Kabul should seriously deliberate as to why all those Afghans who are favorably disposed toward peace and toward Pakistan are systematically being removed from the scene and killed," said Pakistan's Foreign Ministry in a written statement issued on Sunday.
Critics have accused the Pakistani government of protecting Taliban leaders to maintain good relations with the group in anticipation of Western forces' eventual withdrawal from Afghanistan _ an allegation denied by Pakistan.
Many analysts also believe the Pakistani intelligence agency's alleged support for insurgent groups is an attempt to promote Pakistan's interests in Afghanistan and counter the influence of archenemy India.
On Tuesday in New Delhi, Afghan President Hamid Karzai signed a strategic partnership with India, which could further strain Afghanistan's relations with neighboring Pakistan.