Lieutenant General David McKiernan's comment in an interview with CNN was the most unambiguous statement yet on the matter by a senior US military officer, reflecting growing US frustration over the insurgent violence in Afghanistan.

"Do I believe that the Pakistani government must do more? I absolutely do. Do I believe there has been some complicity on the part of organisations such as the ISI over time in Pakistan, I believe there has been," McKiernan said on Thursday.

His comments coincided with a political crisis in Islamabad where the ruling coalition said it will seek the impeachment of President Pervez Musharraf, the country's former military leader and long-time US ally.

And it follows reports that the CIA's number two, Steve Kappes, recently confronted the Pakistanis with evidence of ISI involvement with an insurgent network led by Jalaluddin Haqqani.

The New York Times reported last week that intercepted communications provided the Americans with clear evidence that the ISI was involved in a July 7 suicide bombing at the Indian embassy that killed about 60 people.

It has long been assumed by US officials that elements of the ISI has maintained ties with the Taliban and other militant groups it helped create to fight the Soviets in Afghanistan and the Indians in Kashmir.