"The ISI provide financial support (to extremist organisations). It provides technical support. It provides physical support. The Pakistan officials are allowing the safe havens to operate," a defence official told PTI on condition of anonymity, as he is not authorised to speak to the media.
According to Pentagon officials, the US has confronted Pakistan with "concrete evidences" of links between the ISI and extremist organisations like the Haqqani network and Lashkar-e-Tayiba, before it launched a frontal verbal attack on the notorious spy agency for its terror ties.
A second defence department official said that Pentagon has been providing such evidences to Pakistan "since ages" but it is only after the recent attack on a hotel in Kabul and the US embassy in Kabul that crossed all limits, the US defence department decided to go public.
The senior defence official maintained that these evidences gives concrete proof of the relationship between ISI and the extremist organisations including Haqqani network and LeT.
However, the official refused to give further details of the type of evidences that the US has provided to Pakistan, based on which Admiral Mike Mullen, chairman of the Joint Chiefs of Staff, told a key Congressional committee, last week that the Haqqani network "acts as a veritable arm" of Pakistan's ISI.
Officials said Mullen shared his thoughts and text of his remarks with Defence Secretary Leon Panetta (former CIA chief), before he went to make such a strong comment against Pakistan in the public hearing before the Senate Armed Services Committee.
"The Haqqani network, for one, acts as a veritable arm of Pakistan's ISI agency. With ISI support, Haqqani operatives planned and conducted that truck bomb attack, as well as the assault on our embassy," Mullen said in his testimony before the Senate Armed Services Committee.
"We also have credible intelligence that they were behind the June 28th attack against the Inter-Continental Hotel in Kabul and a host of other smaller but effective operations," he told lawmakers last week.
Captain John Kirby, spokesperson of Mullen, said that the chairman stands by his statement, as he believes that all that he said is nothing but truth. "Over the course of the last few years we have shared with the Pakistani leaders the indications that we have about this short of complicity (with extremist organizations in the region including the Haqqani network," Kirby said.
"I am not going to get into now the specifics of all that. But that information has been shared with Pakistan," Kirby said adding that Mullen and the Pentagon stands by everything the Admiral said at a Congressional briefing last week in which he alleged that the ISI of Pakistan provides supports to the Haqqani network.
"We provided in the past examples of how we know this complicity continues to exist," Kirby said.