"Pakistan's intelligence agency continues to support the Haqqani Network and other terrorist groups that are killing US and Afghan forces in Afghanistan, and the vast majority of the material used to make improvised explosive devices originates from two fertilizer factories in Pakistan," Senator John McCain said.
The Republican presidential candidate in 2008 election, McCain said all Americans are deeply saddened by the tragic loss of Pakistani soldiers in cross-border air attack.
"I fully support NATO's commitment to investigate this tragedy thoroughly and immediately. It's important to note that certain facts in Pakistan continue to complicate significantly the ability of coalition and Afghan forces to succeed in Afghanistan," he said.
Later in an interview to Fox Business, McCain noted that Pakistan has every reason to be angry at the killing of its troops, but argued that such things do happen in war.
At the same time, the Senator stressed that the US too was angry with Pakistan on a number of issues.
"I think they should be angry whenever something like that happens and it's a tragedy and we have expressed our condolences and the military commander there, our ambassador and everybody here regret it enormously.
"But the fact is, we are in a war, these things happen in wars, as tragic as it is. We also have many reasons to be very unhappy with what the Pakistanis have been doing, including the ISI, their intelligence group, supporting the Haqqani network who are killing Americans," McCain said.
"Including the fact there was another story just last couple of days about these two major fertilizer factories in Pakistan. Their product is exported and it's quickly turned into the basic material for the IED's that have killed and maimed Americans and Pakistan fails to do anything about that," McCain said.
"Again, we feel terrible about the loss of life.
Hopefully our relations will improve. We give them billions of dollars in aid as you know, and that is under careful examination here in the Congress," McCain said.
"I would base our relations on the fact that their intelligence agency, ISI is supporting the Haqqani Network, which is killing Americans that's a fact and based our relations on that realism and base our aid on their progress in bringing that situation under control," McCain said.
"Just last week, I didn't have to, but I called mother and father of a young man who was killed, Jonathan McCain, by the way, my name, no relation, who was killed just in the last few days.
That's tough on families and if our ally had something to do with supporting an outfit that had anything to do with killing him, they(Americans) have reason to be outraged," he said.
"So, I think the whole relationship has to be examined, on the realistic basis and aid should be conditioned on what kind of progress they make in bringing that situation under control, which has been out of control for years.
Now, they can cut off supply lines into Afghanistan, which can hurt our ability, they have enormous leverage over us, but at the same time, we have to have a realistic approach to our relationship and we do not look at it through rose colored glasses," McCain said.