Top US defence officials have expressed concerns that some elements of Pakistan's spy agency may be involved in improper interactions with the Taliban and other insurgent groups, Pentagon spokesman Colonel David Lapan has disclosed.

Talking to reporters at the Pentagon, Lapan revealed that US officials were concerned about some elements of the Pakistani Inter-Services Intelligence (ISI) having interactions with insurgents that "may be seen as supporting terrorist groups rather than going after them."

When asked whether the ISI was supporting terrorists, he said, "I don't want to go that far, and that's why I said interaction ... Elements of the ISI might be interacting with terrorist organizations in ways that aren't consistent with what the government and the military are doing."

The spokesman added that the Pakistani Army Chief, General Ashfaq Parvez Kayani, himself a former spy chief, was aware of the US' concerns over the ISI agency and shared some of them.

"The ISI has done a great deal in fighting terrorism ... but we also have some concerns with ... the strategic focus of the ISI," he said.

Lapan's comments followed a newspaper report this week that quoted some US officials and Afghan militants as disclosing that some ISI members were pressing the Taliban to field commanders to fight against the US and its allies in Afghanistan.