Pakistan's army chief has dismissed allegations that his spy agency had helped Afghan militants attack the US embassy in Kabul, insisting on Friday that the charges were baseless and part of a public "blame game" detrimental to peace in Afghanistan.

General Ashfaq Kayani's terse statement suggested Islamabad had no immediate intention of acting on renewed American demands that it attack the Haqqani militant faction in their main base in northwest Pakistan. It also ramped up a dispute between the two nominally allied nations that has exposed their increasingly deteriorating relationship.

Admiral Mike Mullen, chairman of the US joint chiefs of staff, accused the army's Inter-Services Intelligence agency on Thursday of supporting Haqqani insurgents in planning and executing a 22-hour assault on the US Embassy in Afghanistan last week and a truck bomb that wounded 77 American soldiers days earlier.

Kayani said in a statement that the allegations were "very unfortunate and not based on facts."

The claims were the most serious yet by an American official against nuclear-armed Pakistan, which Washington has given billions in civilian and military aid over the last 10 years to try to secure its co-operation inside Afghanistan and against al-Qaida.

Kayani's statement appeared to imply that Pakistan's contacts with the Haqqani network were part of efforts to bring it to the negotiating table. The United States, Kabul and European countries all agree that a peace deal will be needed to end the war, though not all agree on whether the Haqqanis, which have links to al-Qaida, should be included.

The statement said that "on the specific question of contacts with Haqqanis ... Admiral Mullen knows fully well which ... countries are in contact with the Haqqanis. Singling out Pakistan is neither fair nor productive."

Kayani, regarded as the most powerful man in Pakistan, said the "blame game" between it and the US should give way to constructive dialogue over the future of a peaceful Afghanistan.

The Haqqani insurgent network is widely believed to be based in Pakistan's North Waziristan tribal area along the Afghan border. The group has historical ties to Pakistani intelligence, dating back to the war against the Soviets in Afghanistan in the 1980s.

Mullen's words marked the first time an American official had tied Pakistan's intelligence agency directly to the attacks and signaled a significant shift in the US approach to Islamabad. In the past, US criticism of Pakistan largely had been relayed in private conversations with the countries' leaders while American officials publicly offered encouraging words for Islamabad's participation in the terror fight.

Mullen did not provide specific evidence backing up his accusations or indicate what the US would do if Pakistan refuses to cut ties to the Haqqani network.

The US has repeatedly demanded that Pakistan attack the insurgents and prevent them from using the country's territory.