Taliban and al Qaeda militants operating in the Afghan border region are shifting their focus to Pakistan and are working together to hit the forces of that country, a top US military commander has said.

Commander of the Task Force in Afghanistan Major General David Rodriguez also said the Taliban in Afghanistan probably will not stage a spring offensive in the volatile eastern region bordering Pakistan.

"In the last couple of months here, several insurgent leaders have declared war against the government of Pakistan, just like they had done against us several years ago," he said on Wednesday.

"I think that many of them are coordinating with each other more and more based on their short-term goals rather than their long-term goals. They'll move where the best opportunity has to get the highest payoff. And right now that probably seems to be in Pakistan."

Asked specifically to acknowledge that coordinating with each other meant the Taliban and the al Qaeda, Rodriguez said: "Yes, and there are several other organisations and everything, yes, but they're doing more coordination and more trading off of everything from resources to intelligence and technical expertise."

The senior American military commander argued that as far as their ability to protect themselves is concerned, the Pakistani military trying to do the right thing.

"They are working, for example, to develop a better capacity to do counterinsurgency operations, like many other nations are, because that has not been their forte on what they've been trained on," he said.

"They're (Pakistan) adjusting their military now to do those things. But they're committed to do the right thing, and they're going to continue, I believe," Rodriguez said.

He said the infiltration across the porous Afghan border has been a little bit down lately.

"That's due to several reasons. One, of course, is the instability in what's going on in Pakistan and some of the challenges that are going over there, going over in Pakistan.

We've had some success on the border interdicting some of the enemy that had crossed over there.

"The Afghan national security forces and the Afghan border police, there are more of them there than there were last year, so they're able to interdict a little better. The weather that makes it that much tougher during this time of year to infiltrate across there," Rodriguez said.

He also said he sees no sign that the US is preparing to send forces into Pakistan without Islamabad's approval.

"Pakistan is a sovereign government, and we have no plans that I'm involved in or have even heard of to do anything like that."

"We have great military-to-military coordination with the Pakistani military on the border. Over the years, the coalition forces have been able to develop some improving trust between the Pakistani military and the coalition forces, and now that is starting to extend to the Afghan military forces," he said.

The Pakistani military leaders realise "it's a common enemy that we're fighting," he added.